Friday, December 05, 2008

Radiant Floor Heating For Comfort And Efficiency

Radiant floor heating is an efficient and comfortable way to heat your home. It provides superior comfort to compared forced air heating because the heat emanates from the floor, and rises. The air cools somewhat as it rises. This allows the temperature at the feet and legs to be slightly warmer than the temperature in the air around the head.

Radiant heat is produced from either hot water flowing through a pipe system in the floor (hydronic), or by electricity. Hydronic systems are more complicated to install than electric systems, because the pipes need to be set in the cement under the floor. Obviously, this is expensive to install, but hydronic floor heating has it's advantages over electric heating.

The water holds the heat much better than electric wiring does, and as a result, is more efficient. It also allows for a variety of ways to heat the water itself. You can use gas, propane, oil, electric or even solar heat. Any traditional heating method is a usable option for heating the water that runs through the underfloor tubing.

Electric heat functions like an electric blanket. As electricity flows through the wiring, it encounters resistance, which causes the wires to produce heat. This is much less expensive to install than hydronic heating. It's easy to find floor tiles with the electric wiring built in, ready to just place and install. These are easily available at just about any home improvement store.

Radiant floor heating is especially popular in rooms that are commonly floored with tile, such as kitchens and bathrooms, but it can be used in any room, or the house as a whole, with any type of floor covering, including hardwood and carpet. It's quite nice to walk into the bathroom on a cold day and notice nice, warm tile on your bare feet. This simply isn't available with forced air heat, unless you keep the temperature uncomfortably warm.

Another advantage of radiant floor heating over traditional forced air heat is that there is no air being pushed through the home. This seems almost obvious, but when air is being pushed through the home it can suck the humidity from the air, especially if there a a leak in the system allowing the dryer outside air to mix with the air being heated.

It also can distribute allergens through the air in your home. Of course, there is also the issue of feeling hot air blasting on you while the heat is on. If you're in the wrong part of the room, it's still too cold. In yet another equally wrong part of the room, you're being hit with hot, dry, allergen carrying air. Neither of these options are particularly comfortable.

Overall, radian floor heating may be a little more expensive to install, but in the long run, it will be a more efficient and cost effective way to heat your home. It will also be much more comfortable. That's a double bonus in my book. I would ask, what's the price you would put on your comfort, but the reality is that it's going to be a big savings in the end.

Alex Parry is the author of a heat exchanger cleaning equipment site, where you can also find more information on shell and tube heat exchanger design

Sunday, November 02, 2008

Avoid Premature Heat Exchanger Failure With Your Furnace

Just as you may have noticed that your automobile runs more smoothly after a fresh new oil change, the same principle works for your furnace, when it comes to a new or clean furnace filter. The main component for both hot water and forced air heating units is called a heat exchanger. The purpose of this nifty component is to take the heat that is produced by burning fuel in your furnace, and to transfer it into the water or air so that it can be distributed through the entire house. The heat exchanger is traditionally concealed from view in hot water heating systems, and is only occasionally visible in forced air systems.

If you look at a modern forced-air gasoline-powered furnace, here is everything that you will find. First, you will find a solid-state furnace control, which has a fan assembly and is visible in the power rear of the furnace. Next, you will find a draft inducer, which provides fan-forced exhaust. Third, you will find both an igniter, and a flame sensor, because your furnace is actually running on firepower. Next, you will find the gas valve and manifold, along with gas burners. On the outside of all of this you will have them, followed by furnace filters or other air filters. Keep in mind, several aspects of this concept will vary based on the model of furnace that you use, though some things will remain the same, including the igniter, the filter of the furnace and the heat exchanger.

The thing that makes heat exchangers malfunction or inoperative in general is the development of a hole, crack or warping that allows hot water to escape, or combustion exhaust to escape into the home's interior air. They do eventually crack or warp over time simply because of the constant heating and cooling that the system experiences throughout the year. However, most heat exchangers can last a significant amount of time, often past their predicted life span depending on whether or not conditions are ideal. Regular cleaning and maintenance of the furnace do play a large part in determining the life expectancy of a heat exchanger, as well as the environment that exists around the furnace unit.

Another heavy contributor to whether or not heat exchangers live out their lifespan properly is reduced airflow, which comes as a result of dirty furnace filters, dirty fan blades, obstructed air vents and dirty duct work. All of these factors contribute to wear on the fan motors, which can significantly reduce the efficiency of the furnace, prematurely burning out them as well. Both fuel-fired and forced-air furnace types are prone to overheating in response to airflow obstructions. Most modern furnaces are built in a way that allows them to shut down if temperatures become unreasonably high based on a dirty or overused filter. However, if the internal temperature elevation caused by dirt and debris is only moderate, the furnace may not switch off but the heat may still be enough to cause metal fatigue to the head exchanger, which can cause serious issues down along the line.

The best way to protect yourself from premature burn out of the heat exchanger in your furnace is to have an annual inspection and a monthly cleaning of your furnace filters. The exam, which should be conducted by a licensed mechanic, should be relatively inexpensive while affording you a great deal of peace of mind. Another useful innovation is the carbon monoxide or CO detector, which is an easy and inexpensive way to protect yourself against exhaust leaks from your furnace.

Bill Whitworth is a professional writer covering home health and safety issues. WEB Products, Inc., is a leading Internet destination for information about furnace filters, air filters, replacement air filters and custom air filters.

Monday, October 20, 2008

Crack Down on Heat Exchanger Fouling

Heat exchangers are the unsung heroes of many industrial processes and as such they tend to be taken for granted - nobody likes paying for what is often seen to be unnecessary maintenance. Heat exchangers provide duty for so long, that when they start to drop in efficiency, it's usually a gradual process that goes largely unnoticed - until their performance has deteriorated sufficiently to be a problem. Then it really is a problem - and one requiring urgent attention.

What aggravates the situation is the heat exchanger that has never been cleaned properly, coupled with the commercial need to keep it on-line. When the decision is made to carry out cleaning, often nobody knows what the performance of the exchanger is meant to be, either because the drawings have been lost, or no record of any improvement was made after the original cleaning.

When the exchanger finally is opened up to ascertain the extent of the fouling, it's not surprising to find it is so severe that cleaning takes a lot longer than planned. Any benefit that might have been gained by a quick traditional clean is offset by the extended cleaning duration and costs - and, of course, lost production.

If that sounds like a nightmare scenario, bear in mind that this is the sort of situation specialist cleaning companies encounter every week. Cleaning is often carried out without any firm knowledge of how much of an improvement the cleaning will give and how long its effects will last. Having to make 'finger in the wind' predictions clearly is not a satisfactory way to plan maintenance.

One of the most popular and widely-employed heat exchanger configurations in industry, is the straight or hairpin shell-and-tube exchanger. With hundreds or thousands of small-bore tubes bundled together, the extent of quite modest scaling can involve major work to return the exchanger to anything near its commissioned performance. If the outside of the bundle is heavily scaled as well, the cleaning challenge rises by an order of magnitude.

There is potential to bring about a significant improvement in heat exchanger accessibility and 'cleanability', by working more closely with the people who design heat exchangers and fabricate industrial plants.

Better design would lead to improved cleaning - where improved means faster, cleaner and safer, possibly in-situ or even on-line and with better waste containment. It would then be easier and quicker to clean exchangers back to bare metal to return them to duty and their design performance faster.

Plants are generally specified and ordered on the basis of throughput, not accessibility and ease-of-cleaning. Suppliers are happy to comply with this and therefore tend to design heat exchangers with 30-40% excess capacity to ensure that they can continue to provide duty, even when quite extensively fouled. Heat exchangers the world over are currently designed and installed with a view to using one of three systems for cleaning: chemical, pressure jetting and/or mechanical and this approach has remained unchanged for over 50 years.

When it comes to maintenance, refineries - like most of industry - tend to compete on the same basis - a 21-day shutdown is decreed because it's been done that way for maybe the last 20 years. The same cleaning methods are generally used slavishly, with high-pressure water as the cleaning medium.

Most companies look at their heat exchangers in isolation and simply try to extend their run-time, instead of having them designed or re-designed so they can be cleaned more regularly, but faster and better. BP's Coryton refinery, for instance, managed to reduce cleaning time on one shell-and-tube heat exchanger from three days to three hours by applying a different approach to cleaning it.

If a plant is optimized for cleaning, almost full production can be maintained throughout the cleaning process. Relatively minor mechanical changes, such as adding isolating valves to heat exchangers, means that each exchanger, or bank of exchangers, can be taken down and cleaned while the others remain on-line. A redesign of the exchanger so that a header can be removed, means it can then be cleaned with a different system to the standard high-pressure water jetting, in a few hours instead of several days.

At Dow Corning's silicone plant in Barry, south Wales, a tubular boiler and fire tube in the Energy Recovery Unit (ERU) required the removal of a 5mm layer of deposit in as short a time as possible to minimize lost production. Another obstacle was that the unit, which carries waste gases, takes 48 hours to cool and prepare - even with the introduction of a chilled nitrogen purge - before personnel can enter to clean it manually.

The solution involved developing a bespoke remote de-scaler, which was inserted through a small 50cm man-way. Once inside, the de-scaler expanded to fit the hot fire tube, while reaching the full length of the carbon steel tube. With cooling time and man entry eliminated, the shutdown was reduced from five days to three and there was a noticeable improvement in performance of the ERU when it came back on line.

Improved cleaning cycles also mean the rate of future fouling build-up is reduced, which in turn reduces the risk of tubes corroding as a result of the exchanger being open to the atmosphere longer for cleaning.

Heat exchange surfaces therefore remain smoother and provide better heat transfer. If and when the exchanger does foul up, it's easier to clean next time around, using whichever system is preferred. This would represent a change of practice to what has been the norm since the 1980s, for instance, when what was then Mobil in the UK was one of the first refineries to decide that it would extend run-times by abandoning the annual clean and only clean every two years.

Today, typical service intervals have become stretched to three and even four years in some cases, but the apparent operational savings are actually a false economy. Shareholders are indeed happy, because they are getting longer run times, while competing refineries have little choice but to play the same game or lose millions during more frequent shutdowns. Four years down the line, however, the plant will have to come down for major cleaning and maintenance and it will experience a far higher capital replacement cost than ever before.

Mike Watson, Managing and Technical Director

Run by its founder and inventive visionary Mike Watson the company is supported by a wealth of hand selected department managers. With many years experience in developing engineered solutions to complex problems in industry, Mike’s belief is that convention should always be challenged in order to find a better way to achieve improved results. This “never say never” approach, led to him founding Tube Tech in the 1980s. Today, the company cleans the toughest cleaning projects the world can throw at it. Mike often says “If people say it can’t be done, its like a red rag to a bull to me. I will always find a solution”. Mike continues to invest in new technology development, leading the world in new cleaning methodology.

Article Source: http://EzineArticles.com/?expert=Mike_Watson

Friday, October 17, 2008

What is a Fireplace Heat Exchanger?

A furnace centrally heats most homes today so their fireplace does not need to be the main heat source. If more heat output is required then homeowners should look at a fireplace with a fireplace heat exchanger or glass front. These allow more heat into the room based on their design.

A fireplace heat exchanger can be for either a wood burning or gas fireplace. The United States Department of Energy indicates that by using an exchanger you can increase the overall heating performance of the fireplace by five to ten percent. They recommend that this feature be added during the initial installment of the fireplace, but not all contractors agree with this statement.

A fireplace heat exchanger uses a fan to heat the air by pushing it through hot tubes. The tubes then allow the heated air to continue to circulate rather than relying on the process of natural convection. It is important that the exchangers be cleaned frequently because soot accumulates in the tubes. This accumulation will affect the performance of them.

Another term for a fireplace heat exchanger is a blower. The heat exchanging tubes wrap around the fire. The blower will draw the room air in and then returns the fire heated air back into the room. This apparatus will fit into the existing fireplace and if needed can be adjusted by using a trim kit so that it fits properly. If you do not know whether you need a chimney liner for the exchanger then consult your local building codes accordingly.

As mentioned earlier, both gas and wood fireplaces can use a fireplace heat exchanger. The natural gas style fireplace circulates heat by convection and radiation. Radiant heat transfer heat to solid objects but not the air around you. When referring to solid objects, that means anything such as people, walls and furniture as well. Radiant heat allows you to feel warm but the air around might not feel warm. Therefore, the hotter your fireplace gets, the more radiant heat will circulate.

We provide information on all things related to fireplaces such as a fireplace heat exchanger, ventless fireplaces and fireplace rugs along with many other items concerning your fireplace.
by D. Karlson

Tuesday, October 07, 2008

What is a Fireplace Heat Exchanger?

A furnace centrally heats most homes today so their fireplace does not need to be the main heat source. If more heat output is required then homeowners should look at a fireplace with a fireplace heat exchanger or glass front. These allow more heat into the room based on their design.

A fireplace heat exchanger can be for either a wood burning or gas fireplace. The United States Department of Energy indicates that by using an exchanger you can increase the overall heating performance of the fireplace by five to ten percent. They recommend that this feature be added during the initial installment of the fireplace, but not all contractors agree with this statement.

A fireplace heat exchanger uses a fan to heat the air by pushing it through hot tubes. The tubes then allow the heated air to continue to circulate rather than relying on the process of natural convection. It is important that the exchangers be cleaned frequently because soot accumulates in the tubes. This accumulation will affect the performance of them.

Another term for a fireplace heat exchanger is a blower. The heat exchanging tubes wrap around the fire. The blower will draw the room air in and then returns the fire heated air back into the room. This apparatus will fit into the existing fireplace and if needed can be adjusted by using a trim kit so that it fits properly. If you do not know whether you need a chimney liner for the exchanger then consult your local building codes accordingly.

As mentioned earlier, both gas and wood fireplaces can use a fireplace heat exchanger. The natural gas style fireplace circulates heat by convection and radiation. Radiant heat transfer heat to solid objects but not the air around you. When referring to solid objects, that means anything such as people, walls and furniture as well. Radiant heat allows you to feel warm but the air around might not feel warm. Therefore, the hotter your fireplace gets, the more radiant heat will circulate.

We provide information on all things related to fireplaces such as a fireplace heat exchanger, ventless fireplaces and fireplace rugs along with many other items concerning your fireplace.
by D. Karlson

Sunday, September 28, 2008

Designing An Optimal Heat Exchanger from The Quran

If you think that the heat exchanger text book, software and experience is the only reference for you to design an optimal heat exchanger and heat exchanger tubing, then we should look at this interesting video. It shows in detail and provide valuable message on the ultimate optimal heat exchange design. Check it out:






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Friday, September 26, 2008

Better Heat Exchanger Cleaning Through Technology

Maintenance of a platform's Waste Heat Recovery Unit (WHRU) and similar shell and tube heat exchangers can be an extremely dangerous process. It needs to be disconnected, taken off line, and moved to shore for repair. Shell and tube heat exchangers are made of coiled tubes and can become fouled with carbon deposits. The traditional methods for clearing the blockage include bypassing the fouled unit, cutting off bends and cleaning the tubes, then re-welding the U-bends, and complete unit replacement.

The old methods are becoming more outmoded due to advancements in technology. It is inefficient to bypass the unit. Just as it would be less efficient to run your car with 2 cylinders not firing. This inefficiency, of course, also increases operational costs. It is time consuming and costly to cut the U-bends and re-weld them. Sometimes it can be difficult or impossible to get access to reattach them.

Some of these new methods include the ability to clean areas with limited access, and clear deposits from U-bends without ever removing them. This can sometimes be done without even taking the unit offline, and usually takes less time and results in a higher degree of defouling. In fact, many units can be restored to near-factory efficiency. For big refineries, petro-chemical plants, or power plants, this can amount to six figure savings.

The U-bends themselves also retain many deposits, and continue to be a bottleneck to the system. Full replacement carries the cost of completely replacing equipment that, other than the heat exchanger tube fouling, is still in working order. This method also requires the unit be taken offline for the full duration of replacement. obviously this carries a heavy expense and serious loss of production.

Traditional heat exchanger cleaning methods and heat exchanger cleaning equipment have changed very little over the last few decades. Pressure jetting is still the primary means used by many companies, but it is slow, inefficient, and ultimately very costly. Additionally, many companies are skeptical of newer methods, falling back on the "that's the way it's always been done," chain of logic. They are also weary of trying new techniques that are not as "proven" to be effective. Finally, many have long term tube cleaning contracts that do not allow for a change in heat exchanger cleaning technique, unless the contractor were to adopt the new methods.

Newer heat exchanger cleaning equipment and techniques are more technologically advanced, and by extension, require a higher skilled laborer than old style pressure jetting. These new developments include the ability to clean tight radius bends, clean units while keeping them in place, and even while keeping them online. It has also resulted in faster, more efficient cleaning. Many tube bundles can now be cleaned more effectively than with pressure jetting, and jobs that used to take days may now take only a few hours. Difficult to access units are now accessible with these new technologies.

Some of the technology that has been developed includes special nozzles that can be used on tight bends, laser cleaning, and new "smart" metals that respond to changes in density and pressure to prevent damage to the tubes. With these methods, jobs can be finished with less downtime, because cleaning and descaling can be done more quickly. Equipment is also less likely to be damaged in the process. Many of these new processes are safer, create less waste, use no chemicals, and have a significantly reduced environmental impact.

The article was written by Alex Parry who writes about heat exchanger safety at his heat exchanger cleaning equipment site.

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Wednesday, September 17, 2008

Cleaning Plate Heat Exchanger Matter

I made a post entitled "Learning Process From Cleaning Plate Heat Exchanger" which was a follow up entry from "Some Updates". You can refer to the 2 posts for reference. From that post, I received some interesting response and questions from few engineers asking more detail about the cleaning of heat exchangers. The questions are taken from the comment section of that Learning Process From Cleaning Plate Heat Exchanger post without any editing. I answered the questions but I add more of my answers here after thinking about it...

Questions:

I'm a process engineer and your article is very useful and interesting. Could you say (if it possible) how long time did this plate heat exchanger work good without cleaning? And was the concentration of caustic solution high?

Answer:

Thanks for your kind words Olga.

How long time did this plate heat exchanger work good without cleaning?

That depends on how you use the plate heat exchanger and the types and quality of fluid that passes the plate heat exchanger. From my experiences, the plate heat exchanger can operate effectively up to 1.5 years without cleaning, but that is because the feed oil is clean and other combining parameters are good. There are also cases where we have to clean the heat exchanger after 4-5 months... There's no straight answer to this. It depends on a lot of factors. You need to really sit down and monitor the processing parameters and the quality / condition of fluid entering it. I have about 16 plate heat exchangers which I monitored and all of them have different records. Those who belong at the same section in the plant will have almost similar cleaning track record. All of them have different classification of problems too. So, we need to really look at the heat exchanger(s) and make a proper inspection, evaluation and analysis.

The caustic concentration was 3-5%. This also depends on how severe the scale build up is inside the plates. You can have lower concentration if the scale is lesser. You can add up more of the caustic concentration, but it may be not good for your plates (of the plate heat exchanger) or the tubes (of the shell and tube heat exchanger).

Questions:

How heavy and fooling is that oil?

Does it really worth the trouble to use a plate exchanger respect to a shell and tube for such fluids? After all a shell and tube is much easier to clean.

Answer:

It depends on your process and application. What is the type of flow? what is the pressure and temperature? You have to use a shell and tube heat exchanger if you have a high pressure and high temperature. A shell and tube heat exchanger is more expensive. A plate heat exchanger is cheaper and can be used for lower temperature and lower pressure. The main constraint of the plate heat exchanger is because of the gasket used cannot cope with temperature higher then 200oC. so, it's a matter of the effect of process parameters and not the easiness to clean the heat exchanger. A shell and tube heat exchanger 2 pass (or U tube) is also sometimes very difficult to clear especially at the U bend. You need a special equipment with high pressure of jet water to clear the scale, fouling. In worse cases, you need to introduce a small drill combined with the high jet water, preferably up to 20,000 psi to ensure you eliminate the stubborn scale.

Hmmm...maybe those of you who have other experiences on dealing with heat exchanger cleaning can share it with us here...TQ!

The author of this post is Zaki from
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Saturday, September 06, 2008

Furnace Flue Heat Exchanger - Economizer

This is an interesting video about how to make full use of the energy from a heat source. In this case it is a furnace and it acts as an economizer. The video shows how waste heat from the furnace is used to pre-heat the hot water tank feed reducing the amount of energy required and the GHG emissions released. Check it out...



Heat Exchangers for Outdoor Corn Boilers

A heat exchanger is a device designed to efficiently transfer the heat from one medium to another. In the case of an outdoor corn boiler, these media would be air and water.

A typical domestic setup would include a water-to-water heat exchanger for hot water and a water-to-air heat exchanger for forced air home heat. Water-to-water heat exchangers are also used to heat hot tubs, swimming pools and the water for radiant baseboard or radiant in floor
heating systems.

Water-to-Water Heat Exchangers

The three most common types of water-to-water heat exchangers used with outdoor
corn boilers are: Sidearm, Shell and Tube, and Brazed Plate. What differentiates these heat exchangers, besides the cost, is the way they're designed to transfer heat from one medium to another and the method used to create turbulence.

A key component in the efficient transfer of heat between liquids is turbulence. The more turbulent the flow of water through a heat exchanger, the more efficiently heat is transferred.

Sidearm Heat Exchanger

The sidearm heat exchanger is a popular and inexpensive choice for heating domestic hot water. It incorporates a pipe within a pipe design where the water in the inner pipe (your hot water) is heated by hot water from the boiler circulating through the outside pipe.

Turbulence is created by scrolling on the outer surface of the inside pipe.

This straightforward design prevents clogging by sediment and resists scaling. One drawback of the sidearm heat exchanger is reported slow recovery under heavy use. Cost: $130-$150.

Shell and Tube Heat Exchanger

Shell and tube heat exchangers are available in dozens of tube configurations and sizes ranging from a few feet long to 50 feet or more for power plant steam generation.

A variation on the shell and tube design is shell and coil where a helical (spiralling) coil
replaces the tubes.

No matter what the design or application, the basic principle is the same. The water to
be heated flows through tubes, and the heated boiler water, encased by the shell, flows around the tubes.

Turbulence is created by the baffles holding the tubes together in what is called a tube bundle.

Shell and tube heat exchangers for non-chlorinated water applications, such as domestic hot water and hydronic heating, are usually constructed with a brass shell and copper tubes.

For swimming pools and spas the shell should be PVC or stainless steel with stainless
steel tubes. 316L grade stainless steel is commonly used for this application.

Cost: $200-$600 depending on copper or stainless construction and the overall size based on the volume of water to be heated.

Brazed Plate Heat Exchanger

The brazed plate heat exchanger combines compact size with a highly efficient design to produce a device for heat transfer that is up to six times smaller than a shell and tube heat exchanger of similar capacity.

The key to this efficiency lies in their unique construction. Corrugated stainless steel plates are brazed together (eliminates gaskets) with every second plate turned 180 degrees. This design creates two highly turbulent fluid channels that flow in opposite directions (counter flow)
over a massive surface area.

Cost: $100-$500 depending on capacity.

Get better outdoor corn boiler information at Alternative-Heating-Info.com

Monday, May 12, 2008

TLC For Your Furnace - Avoiding Premature Failure of Heat Exchangers

Ever notice how your car seems to run better right after an oil change, especially if you wash and wax it? Well, it's the same for your furnace... don't laugh, I'm serious!

The main component of heating units, both forced air and hot water, is the heat exchanger. This component takes the heat produced by burning fuel and transfers it to the water or air for distribution throughout the house. In a hot water system this component is usually concealed from view, and in a forced air unit only 10 to 25% (sometimes it's completely hidden) of this component is typically visible without disassembly.

Cut-away view of a modern forced-air gas furnaceModern forced-air gas furnace:

1. Solid-state furnace control (Fan assembly visible at lower rear)

2. Draft inducer (fan-forced exhaust)

3. Igniter and flame sensor

4. Gas valve and manifold

5. Gas burners

6. Heat exchanger(s)

7. Air filters

(Configuration will vary between models)

What usually makes heat exchangers inoperative is developing a hole or a crack that allows the hot water to escape, or exhaust from the combustion fuel to escape into the interior air of the home. Constant heating and cooling from years of use will eventually cause a heat exchanger to crack, however some last longer than others. Under ideal conditions, many survive well beyond their predicted life spans.

It seems regular cleaning and maintenance play a factor in life expectancy, as does the environment surrounding the unit. Damp environments tend to assist the build-up of rust on the heat exchanger, shortening its life, while dry, clean environments tend to increase the life span of most furnaces.

Reduced airflow...

Dirty air filters and fan blades, dirty ductwork and obstructed air vents can all contribute to wear on fan motors, reduced efficiency and even premature failure of heat exchangers. Fuel-fired forced-air furnaces are prone to overheating due to obstructions to airflow. Modern furnaces are designed to shut down if temperatures become dangerously high... however, moderately elevated internal temperatures caused by dirt, dust and debris may not be high enough to switch off a furnace, while remaining high enough to cause metal fatigue over extended periods of time.

An annual internal inspection by a licensed burner mechanic or gas fitter, including cleaning and testing for exhaust leaks, should cost between $50 and $100. Considering the implications, I'd say that's a real bargain! Why not have your furnace inspected, and treat yourself to some peace of mind? For those of you with gas furnaces or wood stoves, a carbon monoxide (CO) detector ($30-$45) is an inexpensive means of protection against the possibility of exhaust leaks, between inspections.

Copyright Gil Strachan - All rights reserved.

Gil Strachan is a professional home inspector, representing Electrospec Home Inspection Services in east-central Ontario, Canada since 1994. Visit http://www.allaroundthehouse.com to learn more about home inspections.

"The Home Reference Book"

Saturday, April 26, 2008

Explosive Air

Have you considered your air compressor as a potential bomb?

If you have not, then you better!

Although air compressors are built to withstand high pressures, and will have all the necessary relief valves to take care of normal occurring overpressures, explosion involving fire propagation is another matter.

How can a fire occur in an air compressor?

In order to understand the phenomenon of explosion, we have to understand the nature of fire, because, after all, an explosion is a very rapid propagation of fire.

A fire will only start whenever three conditions are met - fuel, oxygen and heat.

An air compressor when operating will have a very rich supply of oxygen already in place - pressurized oxygen.

Where do we get the fuel?

If you use oil lubricated air compressors, the lubricating oil can become the source of fuel. It can also be in the form of carbon dust. Carbon is formed when oil is heated to high temperatures.

How is it possible to have high temperatures to ignite the combustible mixture?

There can be a lot of reasons - lack of lubrication due to oil deterioration, reduced lubricating quality of the oil, oil pump mechanism fault, oil filter choked, worn out parts leading to lessen oil pressures, etc. Whenever there is a hotspot sufficient to ignite the combustible mixture an explosion will occur. That is the extreme case.

Let's see what can happen that can lead to that extreme case of an explosion.

All the above reasons for lubrication failure or deterioration will gradually cause the machine to operate poorly, wear out the moving parts, cause oil spills and carry over of the oil in the air passages and increased heat built-up.

Now comes the cooling part. Is there a lack of cooling? If the high temperatures due to rubbing of parts from the above are not cooled down sufficiently, the heat will build up. The intercoolers play a very important role in removing the heat?

There are also many other reasons for the lack of cooling.

When the heat transfer surfaces have been coated by films of scale or carbon it will definitely affect the cooling process. The heating surfaces may have been reduced due to choked passages for the cooling medium in the heat exchanger. The cooling medium itself may be too hot probably due to a fault in another machine like the cooling tower where the heat can be taken away to the atmosphere.

The flow of coolant can sometimes be the culprit. When the cooling pump fails, or the driving belt snaps there will be a lack of coolant flow. One must also find out whether the valves for coolant have been accidentally closed or not.

Very often, the effects build upon one another in a vicious cycle - poor heat transfer leads to more heat that carbonizes more oil which coats the heat transfer surfaces more...which leads to worse heat transfer...

Therefore use oil lubricated air compressors with caution. If your air compressors have been running for a long time, chances are, your air compressor pipelines may have already accumulated a sizable amount of oil carried over together with the air flow during operation.

Does your air compressor work non-stop? Is the inter-cooler or the after-cooler efficient? Is your compressed air hot? These are the questions you have to ask yourself.

The oil film in the pipes turns to carbon with heat. The oxygen-rich and moist atmosphere inside the pipes can turn the oil into acids that can further deteriorate the oil to form other organic compounds, perhaps some highly flammable products.

It just needs a spark or a hot spot to ignite this.

Boom!!

Did I frighten you?

What you need is good preventive maintenance. An air compressor working at peak condition with good cooling, good lubricating pressures, and good lubricant and good parts should give trouble-free performance throughout its lifetime.

Sometimes the compressor may have reached the point of no return - coated coolers leading to high temperatures that lead to more coated cooling surfaces that lead to higher temperatures... In this case it is safer to discard the compressor altogether and obtain an entirely new compressor unit. It could be more economical - and safer!

If you do that, do ensure that preventive maintenance is done regularly to keep the unit at peak operating conditions all the time.

An explosion in an air compressor can have grave consequences. Don't take any chances. Perform regular preventive maintenance or buy a new unit before an explosion occurs.

Until next time…

Locate good air compressors for your garage and workshop here:
Eastwood

Many years of working experience in Marine, Facilities, Construction has given the author material for writing e-books and articles related to engineering, and management.

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Energy Related Terms Explained

Below are some terms you may encounter while researching energy related products, heating and efficiency:

AFUE (annual fuel utilization efficiency): an efficiency rating that measures the efficiency with which gas and other fossil-fuel-burning appliance use their primary fuel source over an entire heating season. It does not take into account the efficiency with which any component of the system, such as a furnace fan motor, uses electricity. AFUE is expressed as a percentage that indicates the average number of Btu worth of heating comfort provided by each Btu worth of fuel consumed by the system. For instance, a gas furnace with an AFUE of 80% would provide 0.8 Btu of heat for every Btu of natural gas it burned.

Air infiltration: the introduction, usually unintentional, of unconditioned outdoor air into a mechanically heated and/or cooled building. Air infiltration can occur through any opening in the home's structure, including seams where walls meet other walls, window or door frames, or chimneys; holes where wires or pipes penetrate walls, floors or ceilings/roofs; and between the loose-fitting meeting rails of double-hung windows or a door bottom and door threshold. It is one of the major causes of unwanted heat gain and loss, and personal discomfort in buildings.

Alternating Current (AC) - An electric current that reverses its direction at regular intervals or cycles; In the U.S. the standard is 120 reversals or 60 cycles per second; typically abbreviated as AC

Amp - short for "ampere" - this measures the amount of electricity moving through a wire. Most household appliances use 15 or 20 amps of power. Amps are what give electricity its "shock."

Biomass Fuel: Any organic (plant or animal) material which is available on a renewable basis, including agricultural crops and agricultural wastes and residues, wood and wood wastes and residues, animal wastes, municipal wastes, and aquatic plants

BTU (British thermal unit): a measurement of the energy in heat. It takes one Btu of heat to warm one pound of water by 1° Fahrenheit. Btu can be used either to define an air conditioner's cooling capacity (i.e., the number of Btu of heat that can be removed by the system) or a furnace's heating capacity (i.e., the number of Btu of heat that can be supplied by the system).

Chemical Energy - Energy stored in a substance and released during a chemical reaction such as burning wood, coal, or oil.

Combustion - Chemical oxidation accompanied by the generation of light and heat.

Conduction is the transfer of heat through solid objects such as glass, dry wall, brick and other building materials. The greater the difference between the outdoor and indoor temperatures, the faster conduction can occur, increasing a building's energy gain or loss.

Convection is the transfer of heat to or from a solid surface via a gas or liquid current. Where home heat loss and gain are concerned, heat convection is caused by air (gas) currents that carry heat from your body, furniture, interior walls and other warm objects to windows, floors, ceilings, exterior walls and other cool surfaces.

Conversion- A number that translates units of one measurement system into corresponding values of another measurement system.

Cord of Firewood: a tightly stacked pile of wood logs measuring 4' x 4' x 8' (128 cubic feet).

Daylighting is the technique of using natural light from windows, skylights and other openings to supplement or replace a building's artificial lighting system. When applied properly, daylighting can reduce lighting costs. When applied improperly, however, it can not only lead to inappropriate light levels but can also raise the building's cooling costs by introducing high levels of solar heat into the interior of the building. Also see SOLAR GAIN to see how sunlight can affect heating costs.

Direct Current - An electric current that flows in only one direction through a circuit, as from a battery. Efficiency is the degree to which a certain action or level of work can be effectively produced for the least expenditure of effort or fuel. BTU of energy consumed (input) x efficiency = BTU output.

Energy: The ability to do work or the ability to move an object. Electrical energy is usually measured in kilowatthours (kWh), while heat energy is usually measured in British thermal units (Btu).

Energy Efficiency - Refers to activities that are aimed at reducing the energy used by substituting technically more advanced equipment, typically without affecting the services provided. Examples include high-efficiency appliances, efficient lighting programs, high-efficiency heating, ventilating and air conditioning (HVAC) systems or control modifications, efficient building design, advanced electric motor drives, and heat recovery systems.

Emission- A discharge or something that is given off; generally used in regard to discharges into the air. Or, releases of gases to the atmosphere from some type of human activity (cooking, driving a car, etc). In the context of global climate change, they consist of greenhouse gases (e.g., the release of carbon dioxide during fuel combustion).

Heat Content - The gross heat content is the number of British thermal units (Btu) produced by the combustion, of a volume of gas under certain with air of the same temperature and pressure as the gas, when the products of combustion are cooled to the initial temperature of gas and air and when the water formed by combustion is condensed to the liquid state.

Kilowatt-hour (kWh): 1000 watts used for one hour - or any combination of energy multiplied by time that is equivalent to that rate of electrical consumption, such as one watt used for 1000 hours, 10 watts used for 100 hours, or 50 watts used for 20 hours. For example, a 100-watt light bulb left on for five hours each day would consume one kWh every two days. Kilowatt-hour is the primary measure on which U.S. electric companies base most customer billing.

Load Estimate is series of studies performed to determine the heating or cooling requirements of your home. An energy load analysis uses information such as the square footage of your home, window and door areas, insulation quality and local climate to determine the heating and cooling capacity needed by your furnace, heat pump or air conditioner.

Mercaptan - An organic chemical compound that has a sulfur like odor that is added to natural gas before distribution to the consumer, to give it a distinct, unpleasant odor (smells like rotten eggs). This serves as a safety device by allowing it to be detected in the atmosphere, in cases where leaks occur.

Methane -A colorless, flammable, odorless hydrocarbon gas (CH4) which is the major component of natural gas. It is also an important source of hydrogen in various industrial processes. Methane is a greenhouse gas.

Operating Cost is the day-to-day cost of operating an appliance, based on energy use.

Payback period is the amount of time it takes to achieve a full return on an investment. For instance, if a high-efficiency direct vent gas fireplace costs $1000 more than a purely decorative fireplace but would save $500 a year in gas usage, the payback period is 2 years.

Propane (C3H8) - A normally gaseous straight-chain hydrocarbon. It is a colorless paraffinic gas that boils at a temperature of -43.67 degrees Fahrenheit. It is extracted from natural gas or refinery gas streams.

Radiation is a method of heat transfer in which heat is transmitted from surface to surface via infrared waves. Radiant heat warms the surfaces it touches without increasing the temperature of the air through which it travels. All warm bodies radiate infrared energy.

R-value is a measurement of a material's ability to resist heat transfer. Insulation products are rated according to the R-value. The higher its R-value, the greater the product's ability to resist heat flow will be.

Solar Gain is the heat that builds up inside a structure as a result of sunlight that enters through transparent or translucent surfaces, such as windows, and is converted to heat after striking other surfaces inside the building.

Space Heating - The use of energy to generate heat for warmth in housing units using space-heating equipment. The equipment could be either the primary or secondary source of heating.

Thermal Energy - The total potential and kinetic energy associated with the random motions of the molecules of a material.

Thermostat - A device that adjusts the amount of heating and cooling produced and/or distributed by automatically responding to the temperature in the environment. Watt: a unit of electric power. The amount of power required by electric appliances is expressed in watts. Watt-hour is a unit of electric energy, equal to one watt used over a period of one hour.

Volt (V) - The volt is the International System of Units (SI) measure of electric potential or electromotive force. A potential of one volt appears across a resistance of one ohm when a current of one ampere flows through that resistance. Reduced to SI base units, 1 V = 1 kg times m2 times s-3 times A-1 (kilogram meter squared per second cubed per ampere).

Voltage - The difference in electrical potential between any two conductors or between a conductor and ground. It is a measure of the electric energy per electron that electrons can acquire and/or give up as they move between the two conductors. This is how electricity gets from the power plant to your house: high-voltage transmission lines carry the electricity under greater pressure to carry it long distances, while lower-voltage power lines serve individual homes and businesses.

*Article contributed by Karen Duke, Victorian Fireplace Shop

Karen Duke is a fireplace, chimney and hearth industry expert of over 25 years in both the retail and service sectors. She is a CSIA Certified Chimney Sweep and has numerous hearth industry certifications. She is the founder and webmaster of http://www.TheFireplaceChannel.com and she is the co-founder and webmaster of http://www.TheVictorianFireplace.com , which is one of the largest online fireplace retailers in the world. She makes her home in Mechanicsville, Virginia. Karen's contact information can be found on either of the above sites.