Application effect of sensible heat recovery ventilation system in closed rabbit house of North China in winter

Abstract: The contradiction between heat preservation and ventilation usually exists in enclosed breeding rabbit houses without heating in North China during winter. The morbidity and mortality rate of young rabbits in this style barn with low feeding density increased if the temperature fluctuated greatly due to conventional ventilation. In this study, a sensible heat recovery ventilation system (SHRV) is developed to solve these problems. The air quality, energy-saving and ventilation effect of SHRV operation or without ventilation in rabbit house during daytime are studied. Meanwhile, the distribution of the temperature and airflow of SHRV with uniform openings air supply or at the end of duct in the rabbit house are compared and analyzed. An enclosed breeding rabbit house without heating rearing 315 rabbit does and 1 095 fattening rabbits was used as experimental rabbit house. The experiments were carried out from December 2015 to January 2016. Two SHRV were installed and operated from 8:00 am to 16:00 pm. The results showed that when no ventilation existed in rabbit house, the average indoor temperature was 8.91 ℃, the concentration of NH3 and CO2 increased from 7.28 mg/m3 and 0.33% to 15.02 mg/m3 and 0.33% respectively with the increase of indoor temperature, and this indoor environmental condition during daytime is harmful to the health of rabbits. No significant fluctuation of indoor temperature was found when SHRV with uniform opening air supply in the rabbit house, the average indoor temperature was 8.11 ℃, meanwhile, the concentration of NH3 and CO2 dropped from 9.91 mg/m3 and 0.23% to 4.24 mg/ m3 and 0.09% respectively after the SHRV working for 3 hours, and maintained of 4.42 mg/m3 and 0.10%, the relative humidity in rabbit house was decreased from 84% to 56%. When the outdoor temperature fluctuated within -6－5 ℃, the temperature of supply air was increased by 3.4 ℃ after passing through the heat exchanger of SHRV, the average sensible heat recovery efficiency and the coefficient of performance of SHRV were 65% and 5.1 respectively, which reached the national standard of energy-saving with the value of 60% and 2.5 respectively. Compared with air supplying at the end of duct, SHRV with uniform openings air supply will reduce the average wind speed below 0.2 m/s, the temperature difference and wind speed difference were lower than that of SHRV with uniform openings air supply. SHRV can resolve the contradiction between heat preservation and ventilation usually existed in enclosed breeding rabbit houses with common building envelope without heating in North China. At the same time, in order to achieve a more ideal energy-saving ventilation effect of SHRV in this situation, it is necessary to use appropriate plate pitch, increase feeding density and strengthen the airtightness of building envelope to improve insulation effect of houses.