Experimental Study On Exhaust Air Heat Recovery System In Public Kitchen

With the improvement of people’s living standard,the requirements for indoor environment are also increasingly high,and the corresponding building energy consumption is also increasingly large,causing great pressure on energy supply and environmental protection.Key factors affecting building energy consumption include: heating,air conditioning,hot water supply,cooking,lighting,etc.Among them,the energy consumption of hot water supply accounts for about 16.4% of the total energy consumption of the building.The temperature and humidity of the exhaust air generated by cooking are very high.If the waste heat is recycled to heat domestic hot water,the energy utilization efficiency will be significantly improved.It is an energy-saving technology with broad prospects and can be applied in nearly zero-energy buildings.In this paper,an exhaust air waste heat recovery system with the functions of water heating and drying was presented.The integrated system was designed with two condensers in series: one was a finned tube heat exchanger located in the drying box,providing heat for drying,the other was a plate heat exchanger used to heat water.In order to test its performance,a set of kitchen equipped with the waste heat recovery system was built and a series of performance tests were carried out.Firstly,this paper expounds the principle of the exhaust air waste heat recovery system in the public kitchen,and introduces in detail the specifications and models of the main components of the experimental prototype,including the smoke exhaust system,the refrigeration circulation system,the water heating system and the drying system.The arrangement of measuring points,measuring instruments and calibration results of thermocouples are introduced.Secondly,the performance test of the experimental prototype was carried out,and the characteristics of the exhaust air in different seasons in Harbin were tested and analyzed.The heat transfer characteristics,heat recovery rate and COP of the system under different functional combinations(water heating alone,water heating& drying)and different cooking methods(stewing and frying)were analyzed and compared.Afterwards,the characteristics of the drying box were tested.The influences of the opening and closing of the return air valve,the addition of the circulating fan on the drying rate of the system and the changes of the temperature and humidity of the air in the drying box were investigated.The performance parameters of the system,such as the drying rate of chopsticks,cotton cloth,sweet potato and so on,wereanalyzed.Finally,based on the experimental data,this paper optimized the experimental prototype,providing a reference of the design and model selection for users in practical engineering.The environmental and economic benefits of several types of water heaters commonly used in public kitchens and the exhaust air waste heat recovery system were analyzed,proving that the exhaust air waste heat recovery system is competitive in the market.