Experimental And Simulation Study On New Unit For Energy Recovery

Applying the technic of exhaust air energy recovery to direct evaporative100%outdoor air unit, which cooling the condenser with low temperature exhaust indoor air, will sufficiently recover energy from exhaust air and meanwhile improve operating condition of the unit. Increasing the air volume of the condenser by mixing outdoor air under the condition of unchanged exhaust air volume, will enhance heat transfer between the condenser and air. Nevertheless, the condenser fan will consume more electricity power and the temperature of the air flows through the condenser will increase at the same time. Therefore, there is a best exhaust air to outdoor air ratio when the cooling capacity of the unit nearly reaches its peak, and meanwhile COP is maximized by avoiding too much condenser fan power consumption.With the speedy development of computer hardware and the theoretical study in related areas, simulation technology has become an important way in product development in the field of refrigeration and air conditioning. Compared with conditional product development way of the combination of experience and experiment, simulation technology can avoid the disadvantage of improve product by large amount of test prototype experiment and has advantages of short development cycle, low development cost and high development efficiency. Therefore, it has very important practical significance and commercial value.The experimental and simulation study on100%outdoor air unit coupled with exhaust air energy recovery was conducted in this paper. The experimental study consisted of best exhaust air to outdoor air ratio and effects of variable outdoor air temperature on operating characteristics of the unit. The experimental data showed that the best exhaust air to outdoor air ratio was3:1, and the technique of exhaust air energy recovery lowered much of the discharge pressure and the discharge temperature of the compressor when the outdoor air temperature was above35℃, and meanwhile raised the COP. Firstly, the theoretical physical property models of R22, moist air and mixed air were established. Secondly, the mathematical model of the compressor was established based the equation presented in ANSI/ARI540; the mathematical models of the condenser and the evaporator were established according to the "steady state distribution parameter method" presented in Ref.64; the electronic expansion valve mathematical model was established based on the empirical method presented in Ref.67, and simulation study on the unit was conducted based on steady state. Lastly, the simulation interfaces of the components and the unit were invented by GUI toolbox operating on MATLAB. The accuracy of the simulation program was tested by comparing the simulation data and the experiment data, and the error was within5%, which meant the simulation program was of high accuracy and could be applied to design and improvement of100%outdoor air unit.