Working for the Benefit of Humanity ... Rather than the "Special Interests"
Information for this article came from the following sources:
Popular Science, December 1970, pages 54-55
Popular Science, August 1973, pages 60-61
Popular Science, February 1975, pages 84-86
Popular Science, August 1976, pages 84-87, 119
Mechanix Illustrated, 1979, pages 112-116
The source materials listed above include photographs, cut-away drawings, and schematics of the ultra-simple Rovac system and its components. This ultra-efficient system could be cost-effectively used in both air-conditioning and refrigeration systems, plus even in heating systems.
The original patents on the Rovac system expired years ago and have become the property of the public domain. It is a shame that the original inventor was hampered virtually every step of the way and never allowed to profit greatly from his valuable invention. Unfortunately, that is life in our modern world.
To prevent any chance of copyright infringement, information from the above sources is below paraphrased and combined into a new, broad-spectrum report concerning the Rovac system and its history, and what appears to be its unfortunate demise. If this report may help revive interest in this amazing system and bring it into use, so be it.
The Environmentally-Friendly Air Conditioning System
IN THE BEGINNING
When the Rovac system was first publicized, there were some who claimed it wouldn't work. Some though it violated physical principles. But in the end, all the doubters were proven wrong. The high-efficiency Rovac air conditioning and refrigeration system is extremely simple in both concept and operation, and uses nothing but ordinary air within the system in the process of creating cooling.
SYSTEM CHARACTERISTICS
The Rovac system does not present any form of environmental or safety hazard. It is an extremely clean system which does not contain any environmentally-damaging products. In this, it is different from our common Freon-based refrigeration systems. Plus, the Rovac system is compact: more so than Freon systems. It also does not contain a poisonous gas, as do ammonia absorption refrigeration units, like those used in many recreational vehicles.
In standard refrigeration systems of either Freon or ammonia absorption types, a small leak anywhere in the system soon results in a total loss of performance, or even worse. An ammonia leak could be detrimental to the health of individuals, especially in a confined space. In the Rovac system, a small leak only results in ordinary air mixing with air. A small leak will also not cause a drastic reduction in performance in a Rovac system: even if left unrepaired over time.
THE ENVIRONMENT
It is time to consider the way we are doing things in our current methods of cooling and refrigeration, and how it can affect our environment. Today, there is much concern about depletion of the ozone layer by various fluorocarbon substances, one being Freon. This substance is commonly used in modern refrigeration systems. To eliminate all environmental concerns, it would be relatively easy just to switch over to environmentally-friendly Rovac systems.
SYSTEM SIMPLICITY
The Rovac system is extremely simple. It does not need the complex, sensitive, and expensive control systems used in our modern air conditioning and refrigeration systems. The Rovac system is truly simplicity at its best. There are no high-pressure seals or high-pressure piping in this system. There is no receiver tank, expansion valve, Freon, condenser, or evaporator in this super-simple system. In this special system, there is nothing to cause a problem by leaking, sticking, or hanging up. One single moving part, the rotary-compressor, makes the whole system work.
The rotary-compressor functions as both the pump and air blower in this unique system. The Rovac system has no complex controls which can fail. It requires no sophisticated equipment to service it. Therefore, this system is very inexpensive for the consumer to maintain. And best of all, the price of the natural refrigerant, plain ordinary air, is very hard to beat. Furthermore, this refrigerant is environmentally-safe, and can be breathed all day long without causing any harmful effect to humans or animals.
PHYSICAL PRINCIPLES
There are some very simple, yet very important physical principles which need to be considered. When air is compressed, it is heated. The quicker it is compressed, generally speaking, the higher will be the temperature which the air attains. Then, looking the other direction: when air is expanded, it is cooled. The faster it is expanded, generally speaking, the cooler it becomes. These are two of the simple principles upon which the Rovac system operates.
THE INVENTOR AND HIS SYSTEM
Now an introduction to the inventor of the Rovac system. Dr. Thomas C. Edwards was only 27 years old when he hand-built his first rotary-compressor. At this time, he was completing his doctorate at Purdue University. His very simple system could draw in air at roughly 81°F and spew it back out at 4°F. The system was dubbed ROVAC, which stands for Rotary Vane Air Cycle.
A SPECIAL SYSTEM
There is a simple principle to note about the Rovac system. The hotter the temperature of the air which enters the inlet of the compressor, the hotter will be the temperature of the compressed air which leaves the outlet of the compressor, as it heads for the heat exchanger. In the Rovac system, if the inlet air temperature is 110°F, the temperature of the pressurized air leaving the compressor will be about 285°F.
There is yet one more simple principle to note about the Rovac system. With a greater temperature differential between compressed air at the compressor outlet and outside ambient air, the Rovac system can work even more efficiently at cooling. Why is this? It occurs because there is a greater heat differential for the heat exchanger to work with. The greater the heat differential, the easier it is to, and the quicker the system can, transfer heat to the outside air.
EARLY CLIENTELE
One of the first users of the Rovac system was J.B. Systems of Colorado. Their intent was to use the system in private airplanes as a very safe cabin heater. It should be noted that current cabin heaters use exhaust-heated exchangers, that can cause carbon monoxide poisoning to the occupants if there is an exhaust leak in the system. But, a Rovac system would not pose any sort of safety or health threat when used as a cabin heater or as an air conditioning system.
In the automotive arena, Chrysler successfully tested the Rovac system in some of their vehicles, under extreme conditions. The system was also thoroughly tested in refrigerated trailers for semi-trucks. The Air Force contracted to test the system for cockpit cooling in fighter planes. The Navy tested the system for use in underwater devices.
In the 1970s, there appeared to be much interest in the Rovac system. This stands to reason, for there should have been even a lot more interest, for such an amazing system. This is a very simple, yet very effective and important system. It was also an environmentalists dream come true.
A SUPERIOR SYSTEM
A Rovac system is able to provide instant, low-cost heating or cooling wherever it is needed. To indicate its effectiveness: in one Chrysler test performed in the blazing Florida sun (yes, under muggy Florida conditions), five occupants (including engineers) rolled down a road for ten minutes in the overheated passenger compartment of a Dodge Coronet.
The Chrysler group wanted to make sure they could get the passenger compartment as stifling hot as possible. They wanted it truly "heat-soaked." The inside temperature of the compartment reached 107°F, with a 70-percent relative humidity. Then came the true test for the worth of this special Rovac system.
While driving at 30 miles per hour, the Rovac system was switched on. In the short time of only one minute and 53 seconds, the passenger compartment temperature was reduced to a comfortable 72°F. That is a reduction in temperature of 35 degrees in only one minute and 53 seconds, while the sun was still blazing through the vehicle windows. That is impressive! No automotive Freon system could do that from a heat-soaked condition, or anything approaching it.
INCLUDED MOISTURE
There is also another interesting characteristic to note when using the Rovac system. There is the potential for a major performance improvement in the system by simply using humid air (such as found in Florida). Moisture holds more heat and transfers it better than does dry air. Therefore, in the hot, muggy climates the system will work even better at cooling. It is almost as if nature is controlling and complimenting this system. The more uncomfortable the natural conditions are for the occupants, the better the Rovac sytem can work to increase creature comfort.
It is realistic to use moist air in any Rovac system where the temperature of the conditioned air is kept above freezing. This would apply in virtually all cases involving air conditioning for humans. In such situations, water nozzles have been installed, which spray a fine mist of water into the air ingested into the system. On the other hand, in other settings, additional moisture in the air would not be used or even desired. One such case would be in refrigeration systems for things like food. The non-use of water spray would prevent ice from clogging the refrigeration system.
THE BASIC SYSTEM
The heart of the Rovac system in a relatively simple device called a roto-cooler compressor. This unit has a multi-vaned hub which rotates inside an elliptical housing. The vanes are allowed to follow the elliptical shape of the housing, thereby increasing or decreasing the volume between the vanes and the rotor as the assembly turns.
In a typical situation, room temperature air at about 80°F is drawn into the compressor from the area needing cooling. This air is compressed to approximately 30 pounds-per-square-inch (PSI), which heats it to approximately 250°F.
The heated air from the compressor passes into a very basic finned-tube heat exchanger, which is cooled with ambient air from a simple blower fan. Because of the relatively low pressure used in the Rovac system (about 30 PSI), the wall thickness of the heat exchanger tubes may be relatively thin to facilitate rapid heat transfer. In the heat exchanger, the compressed air is cooled considerably, to near ambient temperature. It is then sent out of the heat exchanger and into the other side of the roto-cooler compressor.
As the cooled, compressed air enters the opposite side of the roto-cooler compressor, it rapidly expands to atmospheric pressure as it is discharged, thus giving back to the compressor about 80 percent of the energy which was initially used to compress it. Furthermore, in the process of rapid expansion, the air and any included moisture is super-cooled to near 0°F. This results in extremely cold air, with ice crystals included, as it leaves the discharge port of the compressor.
TEMPERANCE
At this point, the raw discharge-air is far too cold for use in cooling passenger compartments. In this situation, a tempering valve is installed in the system. This valve mixes warm air with the super-cold air, to adjust air temperature to a comfortable level for all passengers. Because of ice crystals in the outlet air from the compressor, a trap is also used to prevent these crystals from entering the passenger compartment.
In the automotive setting, a typical Rovac system presents a temperature differential of about 50°F between the hot air intake to the compressor and the cold air exhausted from the compressor into the passenger compartment. If the passenger compartment temperature was initially 110°F, it may be cooled to around 60°F. If this is too cool for the passengers, the simple addition of more tempering heat will increase creature comfort. That is how simple this system is.
LOW-SPEED OPERATION
At low engine speed, the compressor is turning relatively slow. That means that air is being compressed and moved through the system relatively slowly. This situation does not allow the system to cool the passenger compartment as quickly as necessary. Therefore, the temperature of the passenger compartment may rise to an uncomfortable level.
To counter this situation, some means of obtaining optimal performance and air movement is needed. During testing of the Rovac system, an auxiliary air compressor was connected to the system to provide improved air flow. This seemed to be one workable answer during low speed operation.
The additional air flow required during low speed operation could also be accomplished by the use of a variable-ratio drive system for the compressor. This drive system would allow the compressor to be over-driven at low engine speeds for increased system efficiency. Then, as engine speed increased, the relative speed of the compressor would be reduced to whatever was necessary to maintain creature comfort.
REFRIGERATED TRUCKS
At this point, let us explore the advantage of the Rovac system when used as the cooling system in a reefer truck. The Rovac system, by itself, does not remove moisture content from the circulated air, as does a standard Freon-type air conditioning or refrigeration system.
All the moisture in the original air is continually recycled in the Rovac system. This helps to prevent things like meat and other foods, plus flowers, from drying out when cooled. It should once again be noted that this drying-out is a common problem when using conventional refrigeration systems.
TECH TALK
Now for a little technical talk. Our common Freon refrigeration systems use a reverse Rankin cycle with a gas-to-liquid-and-back-to-gas phase change. The Rovac system uses no type of phase change in the air. It passes through the system as is. The only phase change which occurs in the Rovac system is the freezing of any included moisture.
LATER HISTORY
When Dr. Edwards left Purdue University, he left the patent rights for his impressive system with the Purdue Research Foundation. He had high hopes that his special air conditioner would soon be produced by the thousands. But what happened?
It is now about 45 years since the first Rovac was built and successfully demonstrated. It is about 40 years since successful testing of the system in motor vehicles. Why do not we see this simple and practical device in common usage today? Did someone "drop the ball" or did someone else pull some strings to block the ROVAC system? Has this system faced unsurmountable obstacles from within the established air conditioning industry?
In about 1973, the Rovac Corporation was established by Mr. Edwards. It was based at Rockledge, Florida. Rovac was soon thwarthed in their attempt to capture the automotive air conditioning market. It appears the automakers attitude is as follows: Flurocarbons are still legal. If fluorocarbons are banned because of their negative effect on the ozone layer, the industry might then switch to the Rovac system as a reasonable alternative.
Fellow citizens, why should we wait any longer, when there is an economical, tested and proven, environmentally-safe system which could, right now, be put in place in automotive, residential and industrial settings? This is an extremely disgraceful and unjust battle which has faced the Rovac system. In the meantime, the consumers and the environment are the ones which are being hurt.
A PROVEN SYSTEM
By February of 1975, Dr. Thomas C. Edwards had worked four long, hard years on his unique system. During this time, it appears that he endured loud put-downs from established giants in the Freon-dependent refrigeration industry. But, by 1979, the Rovac system had proven its great efficiency and potential savings to be had by the consumer, especially in a home setting where much energy can be expended.
HOME IMPROVEMENT
A Rovac heat-pump and air-conditioner unit for a home can operate with a year-round energy efficiency ratio (EER) of more than 6, and possibly even as high as 8. This means a Rovac system can provide 6 to 8 BTUs of heat or cold for each watt of electricity used. Many standard heat pumps have an EER which is just a little more than 5. What does this mean to the consumer?
If you were to pay as little as 5 cents per kilowatt-hour and use 20,000 kw of electricity per year for heating and cooling with a Freon-based heat pump, the Rovac system may save you $150 to $400 per year. Once again, that is figuring at 5 cents per kilowatt-hour. Now, how much are you currently paying per kilowatt-hour? Do the math, and you will begin to see the great savings potential which the Rovac system presents.
ENERGY SAVINGS
In a typical automotive setting, the Rovac system draws only 1-1/2 to 4 horsepower from the engine, compared to about 7 horsepower for a typical Freon-type air conditioning system. What this means is that the Rovac system would help give better overall fuel mileage. This is an important factor, considering our current energy perdicament.
Think about all those vehicles caught in traffic jams on hot summer days. Just think about how much fuel the Rovac system could save our nation. Now consider the savings potential for all the air conditioned vehicles in the whole world. Then there are homes and buildings, and the savings to be experienced in their cooling needs. The total savings, worldwide, could be utterly phenomenal.
MORE TECHNICAL STUFF
A typical automotive air conditioning system has a rating of approximately 5,000 Btu of cooling per hour, with a delivery of 250 cubic feet per minute, and a 20°F temperature differential between inlet and outlet air. The coefficient of performance (COP) of the typical auto air conditioner is only about 0.5 in terms of the work put in by the engine versus the heat removed.
A typical automotive-size Rovac compressor rotating at 1350 rpm delivers over 20,000 Btu of cooling per hour. After all losses are factored in, a Rovac system should have a COP nearly 3 times better (or even more) than Freon-type heat pumps. There is another important factor with the Rovac system. It is also cheaper to build and maintain, than is a Freon-type system.
SOME BENEFITS
Let us look at some of the benefits of the Rovac system.
On a summer day, the Rovac system begins cooling very rapidly from virtually the moment it is turned on. This is very different from Freon systems, which take several minutes to start cooling. During this whole time, the occupants of a vehicle may be sweating profusely in the blazing heat. With a Rovac system, there is no more need to utterly "waste a shower," even under humid Florida conditions.
On a cold winter day, the Rovac system can begin providing heat within seconds of engine start-up, for use in passenger compartment heating and window defrosting. This is very different from our present heating and defrost systems which take a long time for the engine water temperature to raise to a usable level, for heating and defrost, during cold weather.
Let us consider this cold-weather characteristic of the Rovac system. In a standard automotive system, when the windows are fogged or frosted, the driver may sit with the engine running for quite a period of time, waiting for the windows to defog or defrost. With the Rovac system, the windows may be defogged or defrosted rather quickly. This will allow a driver to safely begin driving sooner, which will save fuel. Considered nationwide: this could save a lot of fuel.
Then there is another benefit with the Rovac system. There is no high-pressure, environmentally-harmful gas stored in this system. Because this system uses just ordinary air in its cooling process, there is no chance for contributing damage to the ozone layer, or creating any other problem, if there is a leak in the system.
COST CONSIDERATIONS
Let us now examine some of the cost-reducing benefits of the Rovac system, compared to our commonly used systems:
1) There is no high-pressure, environmentally-damaging gas at approximately 300 psi used in the Rovac system, as is done in our current systems. Therefore, no high-pressure seals are used. The use of simply low pressure air in a ROVAC system reduces overall cost. As a bonus, in the Rovac system, all sealing problems are eliminated.
2) The Rovac system does not require high-precision tolerances or any perfect sealing in any type of refrigerant-line connections. This reduces the overall cost of ROVAC systems.
3) Manual gas recharging is never required in the Rovac system. The roto-cooler compressor automatically charges the system with the necessary air whenever it is operating. This reduces the initial cost of the system, plus maintenance costs over the life of the system.
4) No complex expansion valve or fragile capillary tube are used in the Rovac system. There is also no costly condenser used. This greatly simplifies and reduces overall system cost.
5) The heat exchanger tubing is of a large diameter, and because no high-pressure is used in the system, the tube walls can be relatively thin. The whole exchanger can also be made relatively simple and small. This reduces overall system cost.
6) No separate blower is needed in the Rovac system. The one moving unit, the rotary-compressor, works to move all necessary air into and out of the system.
7) The Rovac system is a natural for retro-fitting existing vehicles. The labor to install it would be much lower than when installing Freon-type sytems. It is also a much safer system to install and maintain.
IN CLOSING
It is time to bring the environmentally-friendly Rovac system out of the "deep, dark corner" and put it to good use. It is time to begin experiencing the high efficiency this system presents, plus the economic savings which it has to offer.
What are your thoughts on this matter?
A REQUEST
The ROVAC technology does not appear to be common knowledge amongst the general public, even though there were many articles published about it in the 1970s. It is an extremely good technology which, for a period of time, was intermittently flashed upon the public scene and then generally disappeared.
ROVAC technology may be one factor which could help to quickly and inexpensively change our world for the better. It could help to release the general public from bondage to any environmentally-damaging and economically-damaging monopolies.
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