Energy-saving Analysis of Runner-type Energy Recovery Device

Aiming at the contradiction between increasing fresh air volume and air conditioning energy, combining with the requirement of air heat recovery of building Energy conservation standard in China, this paper takes fan coil unit plus fresh air conditioning system in the summer as the research object, and discusses the energy conservation effect of runner energy recovery device (AAERE). In this paper, the fresh air units and the loads of fan coil unit in several typical ways of fresh air treatment of fan coil unit plus fresh air conditioning system, especially the dry working condition of fan coil unit, were discussed. Under dry condition, fresh air undertakes indoor steady cooling load and all indoor wet load instead of fan-coil units do not take on indoor wet load, which results in large enthalpy difference of fresh air treatment (> 40 kJ/kg) and limits the operation of fan-coil units under dry condition. The changes thermal parameters of surface cooler, enthalpy difference of fresh air treatment, temperature of return water and cooling capacity of chiller before and after using runner-type heat recovery device in a hotel in Changsha were analyzed and calculated. The energy conservation effect of air conditioning system before and after using runner-type heat recovery device in fresh air units were analyzed.

In the calculation example, a KL-2-411000 surface cooler with 4 rows, 10 surface tubes and 1000 mm effective length was selected for the fresh air unit. The heat transfer area of each row of the surface cooler is Fd=31 m2, the cross-section area of water flow is Fw=0.00201 m2, the windward area is Fy=0.430 m2, and the windward velocity is vy=2.3 m/s. The assumed velocity method was adopted, and the flow velocity is 1.0 m/s. The sensible heat energy recovery device with efficiency of 70% is adopted in the fresh air unit. The enthalpy difference of fresh air is 40.1 kJ/kg before AAERE was used and 33.6 kJ/kg after AAERE was used. Before AAERE was used, the supply and return water temperature of fresh air unit is 10.5 ℃ and 16.2 ℃ respectively. After AAERE was used, the water supply temperature of fresh air unit rose to 12.3 ℃ and the return water temperature is 17.1 ℃. The cooling capacity of fresh air unit were 48.72 kW and 40.32 kW respectively before and after AAERE was used, and the saving efficiency is 19.4%. If the runner heat recovery device is used to recover part exhaust heat so as to pretreat fresh air in the new air unit, the enthalpy difference of fresh air and the cooling capacity of chiller are reduced, the water supply temperature and the evaporation temperature of chiller are increased, the cop of chiller and the operation efficiency are improved, that is, the energy consumption of air conditioning system is decreased. In addition, when the temperature of supply and return water increases, the investment of heat preservation of cold water pipeline is saved, the cold loss of system is reduced, and the operation economic benefit is improved.