Study On The Development And Application Of Heat Recovery Ventilation System In Rabbit House

In cold weather condition,rabbit farm have to reduce ventilation rate to maintain acceptable thermal environment or to save energy consumption in rabbit house.Insufficient ventilation greatly threatens rabbit health because of contaminants accumulation in rabbit house.The key to solve the problem is to reduce heat loss caused by high ventilation rate in rabbit house.Heat recovery ventilation(HRV)is of great value for energy conservation in residential buildings.It uses heat/energy carried by exhaust air to preheat supply air through an air-to-air exchanger.The heat load produced by animals is considerable in intensive animal production,and enclosed animal house needs high ventilation rate to maintain acceptable indoor air quality.Both of the factors determine the high potential of HRV application in enclosed animal house.The experiment first studied the feasibility of an integrated heat recovery ventilator for rabbit house application,which were commonly used in residential buildings.The indoor NH3 concentration remained the same level when the HRV were operated in the rabbit house.Besides,installation problems and high cost of equipment also made it not practical for animal house application.Aimed at solving the above problems,work have been done to develope a new heat recovery ventilation system.The new heat recovery ventilation system was tested to fulfill the following important criteria for animal house applicaiton,including high flow rate,low pressure drop,high heat efficiency,less ice formation,less dust accumulation,and shorter pay-back time.The new heat recovery ventilation system was then installed and operated in rabbit house to learn the performance in different climate district,including cold climate in north China,severe cold climate in northeast China,and warm climate in sohtheast China.The software DeST was employed to simulate the effect of climate,envelope insulation,ventilation rate,heat recovery and animal density on air temperature in rabbit house and performance of heat recovery ventilation system.In cold climate zone in north China,operation of the HRV decrease the concentration of CO2 and NH3 by 53%and 48%,respectively.And no significant negative effect was observed on indoor air temperature when the ambient temperature varied from-10? to 10?.The sensible heat efficiency and coefficient of performance(COP)of the HRV were 65%and 5.7,respectively.Both of them met the energy conservation standard in GB.The uniform air supply of the HRV achieved better temperature distribution and created less draft than the one end air supply.In severe cold climate zone in northeast China,the HRV can not operated when the ambient temperature fell below-15 ? for the reason of ice formation inside the heat exchanger.In less cold climate,the ambient temperature varied from-15 0C to 5?.The HRV significantly increased ventilation rate and improved air quality without sharp air temperature drop in the rabbit house,even no extra heat supply was given.In colder climate,the ambient temperature varied from-25? to-5?.A system integrated the HRV with boiler heating was used to heat and ventilate the rabbit house.The incoming fresh air was preheated by the boiler room before it entered the heat exchanger to prevent ice formation.The solution made it possible to operate the HRV in ambient temperature as low as-25?.In hot climate zoon in southeast China,the HRV integrated with air-conditioner cooling was used to cool and ventilate the rabbit house in summer.The system maintained acceptable indoor air temperature of 25 ?-28? for breeding rabbit reproduction.The operation of heat recovery significantly decreased the concentration of CO2 and NH3,only resulted in 1.4? air temperature rise when a consistent cooling capacity was provided.The level of temperature and humidity index(THI)showed that fresh air supplied by heat recovery ventilation had no negative impact on level of rabbit heat stress.The HRV was energy efficient,it achieved sensible heat efficiency and coefficient of performance value of 63%and 3.5,respectively.The HRV was economic to operate when the temperature difference between indoor and outdoor was not less than 5.1?.In simulation study by DeST,a rabbit house thermal balance model was made.The results showed that the weighting factors on rabbit house temperature including building envelope,building tightness,production density,minimum ventilation rate and heat recovery ventilation.The minimum ventilation rate,heat recovery ventilation and building tightness covered 80%of the weighting factor.As the ambient temperature varied from-15 ? to-5 ?,the air temperature in the rabbit hosue with heat recovery ventilator was 3.6?5.9 ? higher than the rabbit house with a normal mechanical ventilation.