Research On The Spiral Tube Condenser And Development Of The Exhaust-source Heat Pump System

Natural gas is a new kind of clean energy which is used by more and more industries, especially in boiler industry. And gas boiler is replacing the pulverized coal fired boiler. The flue gas temperature is very high, many energy waste problems and heat pollution problems are caused if the flue gas is directly discharged into the atmosphere. In order to reduce the flue gas temperature and recover the waste heat of flue gas, the principle of air-source heat pump is used in this paper, and a set of exhaust-source heat pump system is designed. The experiment research and numerical simulated research of the spiral tube condenser are carried out in this paper. The works and conclusions are as follows:(1) Four equipments in the exhaust-source heat pump system are designed according to the flue gas of 1T/h gas-fired hot water boiler, it shows that 39 kW heat of exhaust can be recovered when the temperature of flux gas fall from 80℃ to 50℃, the heat can raise the temperature of 1997 Kg water from 50℃ to 70℃ every hour, and the COP of the exhaust-source heat pump system can reach 4.8.(2) Water is used as the heat transfer fluid and the spiral tube heat exchanger models with different pipe diameter(6mm<d0<14mm)、different thickness of space bar(2mm<S2<4.5mm)and tube pitch(2mm<Z<14mm)are built in this paper, the numerical simulated research about the characteristic of heat transfer and flow in the shell side of spiral tube condenser under the condition of Re=8000~20000 is carried out by using Fluent software in this paper. Through the numerical simulated research, it can be found that:In the range of 6mm<d0<14mm, the Nu of shell side fluid will be larger when the pipe diameter is smaller under the same condition, the Nu of the minimum pipe diameter heat exchanger is 46~51% larger than the largest pipe diameter heat exchanger. The PEC will reach the maximum when the d0=6mm.In the range of 2mm<S2<4.5mm, the Nu of shell side fluid will be larger when the thickness of space bar is smaller uner the same condition, the Nu of the minimum thickness of space bar heat exchanger is 1.6~2.3% larger than the largest thickness of space bar heat exchanger. The PEC will reach the maximum when S2=3.5mm.In the range of 2mm<Z<14mm, the Nu of shell side fluid will be larger when the tube pitch is larger under the same condition, the Nu of maximum tube pitch heat exchanger is 46~51% larger than the minimum tube pitch heat exchanger. The PEC will reach the maximum when the Z=14mm.(3) In order to compare the heat transfer of performance of Y-type and K-type spiral tube condenser, a performance test platform is built is this paper. The experimental results show that: when the Re of shell side water range from 2800 to 13000, the heat transfer coefficient of Y-type spiral tube condenser is 3.4%~17.9% larger than K-type spiral tube K-style spiral tube heat exchanger, the pressure drop of Y-type spiral tube K-style spiral tube heat exchanger is 9.8%~61% smaller than K-type spiral tube exchanger, the resistance coefficient is 9.8~61% smaller than K-style spiral tube exchanger, the heat transfer coefficient of Y-style is 8.7~11.6% bigger than K-style spiral tube exchanger, the PEC of Y-style spiral tube condenser is more than 1,So that the heat transfer coefficient of the Y-type spiral tube condenser is better.