Experimental Testing and Analytical Analysis of a Plastic Panel Heat Exchanger for Greenhouse Heating

摘要

The performance of a plastic panel-type heat exchanger, suitable for greenhouse heating using low-grade (25 to 60 exp 0 C water) power plant reject heat, was investigated theoretically and experimentally. The theoretical analysis showed that a plastic panel heat exchanger would have an overall heat transfer coefficient, U sub 0 , of about 18 w/m exp 2 - exp 0 C compared to about 12 w/m exp 2 - exp 0 C for a fin-tube heat exchanger, under typical greenhouse conditions. Furthermore the plastic heat exchanger would require less fan power due to reduced air pressure losses. The experimental data revealed a similar functional relationship for U sub 0 and air flow when compared with the theoretical calculations, however the experimental values of U sub 0 were consistently larger by 20 to 30%. It was concluded that a properly designed plastic heat exchanger can compete with metal fin tube type exchangers on a performance basis, but the plastic heat exchangers are 3 to 4 times larger by volume. However, because of the lower cost of plastic, a substantial cost reduction is expected. It appears that further study, examining heat exchanger lifetime, performance and costs, is warranted. (ERA citation 05:016068)