Refrigeration & Air Conditioning: Converting Disbelievers
Appliance Design Magazine
Thermodynamic cycle proves the impossible is here and ready to use.
Physics and thermodynamic students are taught that it is theoretically impossible to cool below the wet bulb temperature of air by evaporating water. It’s no surprise, then, that thousands find it hard to believe that a company in Arvada, Colo. has created a thermodynamic cycle that not only can cool to that level, but is also being licensed for use in appliances.
The technology, developed by Idalex Technologies, is called the Maisotsenko Cycle (M-Cycle), named for its discoverer, Dr. Valeriy Maisotsenko.
“The M-Cycle is a more efficient way to transfer heat that uses the properties of evaporation in unique three-dimensional flow patterns,” says Rick Gillan, president of Idalex. “The working fluid stream is fractioned off in increments and cools the remaining working fluid and the product fluid. This process occurs multiple times until all the working fluid is saturated and used. After passing through the cycle to cool air, up to six times more heat is removed than conventional air-cooling processes.”
To understand the Maisotsenko Cycle better, a few concepts should be understood:
Direct evaporative cooling lowers the temperature of air by using the latent heat of evaporation, changing water to vapor. In this process, the energy in the air does not change. Warm dry air is changed to cool moist air. Heat in the air is used to evaporate water. No heat is added or removed, making it an adiabatic process. The enthalpy of the air or energy of the air does not change. Direct evaporative systems vary from 70 percent to 95 percent effective in temperature reduction related to the incoming air’s wet-bulb temperature.
Indirect Evaporative Air Cooling. Thermodynamically, an indirect evaporative air cooler passes primary or product air over the dry side of a plate and secondary or working air over the opposite wet side of a plate. The wet side absorbs heat from the dry side by evaporating water and therefore cooling the dry side with the latent heat of vaporizing water into the air. The air temperature on the dry side of the plate travels in counter flow to the air on the wet side. Ideally, the product air temperature on the dry side of the plate could reach the wet bulb temperature of the incoming air.
Theoretically, the working air on the wet side of the plate would increase in temperature from its incoming air wet bulb temperature to the incoming product air-dry bulb temperature and be saturated. This would require a balancing of the product and working airflow rates with an infinite amount of surface area and pure counter flow.
In practice, it is not possible to have pure counter flow as the air would need to enter and leave from the same sides. This geometry of plate exchangers force indirect evaporative coolers to be in cross flow. The effectiveness of these types of coolers is reported to approach 54 percent of the incoming air wet bulb temperature.
The Maisotsenko Cycle uses the same wet side and dry side of a plate as described in the above indirect evaporative cooler, but with a much different geometry and airflow, creating a new thermodynamic cycle. This cycle allows any liquid or vapor to be cooled below the wet bulb and toward the dew point temperature of the incoming working air.
The M-Cycle utilizes the psychrometric energy (or the potential energy) available from the latent heat in an evaporating gas. The cycle has been realized in a uniquely designed plate-wetting and channel system, which achieves optimum cooling temperatures within a few degrees of dew point for the product air. In addition, the working air is saturated with high enthalpy, accounting for the sensible heat loss in the product air.
The Coolerado heat mass exchanger (HMX) is the first product that has been fully developed that uses the M-Cycle. “It is a logical and affordable place to start since everything occurs at atmospheric pressure, and it is built using common materials paper and plastic,” Gillan says. “Most other applications of the M-Cycle occur at higher temperatures and pressures and require more expensive materials and fabrication processes.”
Gillan says that the concept for the Coolerado Cooler is the result of Maisotsenko’s work and observations of natural occurring phenomena over the last 35 years. “Our team engineered and refined his scientific concepts into the Coolerado Cooler over the past five years,” Gillan says. “As it turns out, refining the M-Cycle was only one of many engineering problems that had to be solved to get here. Other major obstacles included the water distribution system, understanding minerals and how to control scaling, and creating a modular system that can be scaled for most any size application.”
The Coolerado Cooler works by using water to fuel the cooling process. Many people immediately relate evaporative or swamp coolers to this process. Swamp cooling, however, is a much different process. A more appropriate example is to consider how the body, skin and perspiration work together to cool the body. People must drink water to fuel the cooling process for their body. Similarly, Coolerado Coolers evaporate water (analogous to perspiration) from one side of a plastic plate (analogous to skin) that pulls heat away from air on the other side (analogous to the body). By using this concept in the M-Cycle to repeat the process many times on both the working and product air streams, the product air stream can be cooled to low temperatures without adding any humidity.
The Coolerado Cooler draws in 50 percent to 100 percent fresh outside air. Then about 50 percent of that incoming air is split off, saturated with water and used to remove heat from the other 50 percent of air that is conditioned to enter the building. The cooler can be mounted in or around the building, and can use the same distribution ductwork as the heating system if desired.
Currently, several manufacturers are using Coolerado heat and mass exchangers (HMXs), which uses the Maisotsenko Cycle to make appliances. They include:
* Desert Aire, Milwaukee, Wis. is making hybrid Coolerado/refrigeration air conditioners. These units are mainly used in commercial buildings in semi-humid regions. Most of the time, only the Coolerado HMXs are needed for cooling. When the humidity rises, the Coolerado HMXs still perform the bulk of the cooling, and the refrigeration system dehumidifies and adds some additional cooling. In addition, the exhaust air stream from the HMXs, which could be 20Â°F below ambient air temperature, is used to cool the refrigerant compressor and condenser. This system is efficient and has broad application.
* Novel Aire, Baton Rouge, La. is using a desiccant system to dry the air before it goes to the HMXs for cooling. These units are mainly used in high humidity regions where there is on-site power generation. They use the waste heat form the power generation to dry out the desiccant. Dehumidification using desiccants is an adiabatic process that dries and heats the air. It is the opposite of evaporative cooling. The Coolerado HMXs are able to take that very hot and dry air and cool down for comfort applications.
* Mountain States Equipment Company, Denver, Colo. is building large, custom air handlers for commercial and industrial applications. These units have features specific to the application, are cooled with Coolerado HMXs and usually provide heating capabilities as well.
Also, in early February 2005, Delphi signed an agreement with Idalex to be the world’s exclusive manufacturer of HMX. Delphi will manufacture HMX for Idalex and other customers to incorporate into their air conditioning products.
Many applications could potentially benefit from the M-Cycle, but Gillan says it’s difficult to say now what may come about in the future. “It would be like asking someone in the early 1800s who will most benefit from steel,” Gillan says. “Their answer would likely relate to swords, which was why they were trying to master the material. It was impossible to imagine skyscrapers, ships, automobiles and paper clips at the time. Today, swords would not likely make the top 100, or even 1,000 steel lists!”
Though Gillian says he’s not suggesting the M-Cycle will be as ubiquitous as steel, he does believe there are similarities. “Our current focus is applying the M-Cycle to air-conditioning through the Coolerado Cooler. Applications we can imagine today for the M-Cycle include any process that involves cooling, heat transfer, heat recovery, saturation, humidification, air density and air pressure.
“We focus on the cooling aspects of the cycle because that is the first product we’re taking to market. However, the M-Cycle is much deeper than that. For example, the working air stream from the cooler that rejects the heat to the atmosphere is completely saturated, as can be seen from the test results from the U.S. Department of Energy available on the Coolerado Web site. Although it is not as readily apparent, this feat is just as impressive as the cooling abilities of the Coolerado Cooler.”
Gillan adds that the discovery of the M-Cycle will allow people to use water to fuel many processes. It can even be fueled with seawater. Much of the accelerated testing for Coolerado Coolers is done with minerals added to the water to simulate seawater concentrations.
“It is likely that the next, most beneficial application of the M-Cycle will be for use as a refrigerant condenser,” Gillan says. “By applying the M-Cycle to the heat rejection portion of traditional air-conditioners we can nearly double current efficiencies. This is a very important application of the cycle for freezers, refrigerators and air-conditioners that will work in any part of the world.”