Summary
The facility consisted of five greenhouses which together covered 4,000 m2 and an additional small room with a rice-hull burner and two heat exchangers for hot-air and hot-water. A performance test was run with maximum rate of burning while the outside air was -5 centigrade with wind velocity of 5 m/s. Snow covered the ground and the test was run from 9 to 11 p.m. on Feb.25, 1981. The following results were obtained.HomePage
(1) Temperatures of the combusion gases in the burner, at tue entrance to the heat exchanger and at the exit of the heat exchanger were higher than estimated in the original design.
(2) Assuming a rice-hull heat value of 3,200 kcal/kg, 489,600 kcal/h were obtained at the maximum burning rate of 153 kg/h. This gave a burning efficiency of 97.%.
(3) The hot combustion gases caused an expansion of the connecting points between the entrance and the exhaust of the hot air heat exchanger. The expansion caused a leak through which some hot combustion gases escaped. The total heat input to the heat exchanger was estimated to be 487,788 kcal/h.
(4) The heat required to raise the temperature of the air and water was 47.5 and 27.8%, respectively, of the available heat. But the quantities of heat which were actually transferred were 40.2 and 22.2 %. Therefore the eff1cleneles of heat transfer were 84.6 and 80.0 %, respectively. The heat recovered by circulation of the hot-air and the hot-water was 33.7 % and 94.2 % of the heat supplied.
(5) The amount of heat actually transferred to the receiving side of two heat exchangers was 304,443 kcal/h corresponding to 62.4 % of the total available heat. The other 19.8 % of the available heat was waste-fully exhausted to the outdoors. If the wasted heat could be effectively used, the efficiency of heat transfer would improve to 82.2 %.