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Desiccant Dehumidification Technologies
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
Figure 39-14 shows a plan view and Figure 39-15 is a cutaway illustration of a double rotating wheel system, with representative air conditions shown. This system features two wheels. First, the air is dried in the desiccant wheel, then the air temperature is reduced in the second (thermal wheel) before it is delivered to the conditioned space. The second wheel, which is metal, serves as a heat exchanger. Most of the heat from the air leaving the desiccant wheel is removed to preheat the regeneration airstream, thereby reducing the external heat source requirement. As the wheel gives off heat to the incoming air on the regeneration side, it is cooled and rotates back to the conditioning side to extract heat from the hot dry airstream. As shown, outdoor or building exhaust air entering the regeneration side of the system first passes through an evaporative cooler, which cools the incoming air and raises its RH. The cooler incoming air serves to increase the efficiency of the thermal wheel. Figure 39-16shows an installation of this technology in a packaged rooftop unit. Figure 39-17 is an open-case view, showing the rotating wheel.
Air-conditioning principles
Published in Roger Greeno, Building Services, Technology and Design, 2014
The known energy resources of the world are diminishing and conventional fuels cause atmospheric pollution, the greenhouse effect and contribute to ozone depletion. It is, therefore, of paramount importance that energy be reused where possible. High tariffs and taxation alone are insufficient deterrents; science and technology have to combine to develop more efficient fuel consuming equipment. In addition to the condensing boiler, which reuses the flue gases for secondary heating (see Chapter 3), some other successes include: heat pumpheat pipesplate or annular heat exchangerrun-around coilthermal wheel.
Waste Heat Recovery
Published in Clive Beggs, Energy: Management, Supply and Conservation, 2010
The matrix material in a thermal wheel is usually an open-structured metal, such as knitted stainless steel or aluminium wire, or corrugated sheet aluminium or steel [1]. For use at higher temperatures honeycomb ceramic materials are used. Although thermal wheels are usually employed solely to recover sensible heat, it is possible to reclaim the enthalpy of vaporization of the moisture in the ‘hot’ stream passing through a thermal wheel. This is achieved by coating a non-metallic matrix with a hygroscopic or des- iccant material such as lithium chloride [1].
Energy saving in an air conditioning system using modified HVAC unit as an energy reducer
Published in International Journal of Ambient Energy, 2018
G. Mageshwaran, G. Britto Joseph, Tallapaneni Sivaji, Vulchi Ravi Teja, R. B. Durairaj Nithiyanantham
As the thermal wheel rotates, heat is picked up during one half of the rotation from the exhaust air stream, and given up to the fresh air stream in the other half of the rotation. Thus, waste heat energy from the exhaust air stream is transferred to the material matrix and then from the matrix material to the fresh air stream, raising the temperature of the supply air stream by an amount proportional to the temperature difference between the air streams, or thermal gradient, and depending upon the efficiency of the device. Figure 3(a) depicts the AHU with a HRW and its temperature distribution. The temperature variation of the AHU with a heat pipe and a HRW is shown in Figure 3(b); the HRW introduces two more temperature variations; therefore, temperature needs to be measured at seven locations.