Investigation On The Performances Of A Cross-flow Heat Recovery Ventilator

Improving indoor air quality and energy-efficiency has received more and more attentions in many countries. On one hand, thermal loads of buildings, apart from internal gains, can be classified in two main categories: losses or gains through the envelope and ventilation loads. On the other hand, In order to improve indoor air quality, ventilation loads are increasing as following as fresh air supply rates are becoming greater. Therefore, to improve indoor air quality, the energy consumption tends to increase, which is antinomy for us. Among the possible methods, heat recovery ventilator (HRV) is attractive to reduce ventilation loads and has been equipped in many HVAC (Heating Ventilating and Air Conditioning) systems in current days.There are some influencing factors on the performance of a cross-flow heat recovery ventilator (CFHRV) that has cheaper cost of building, manufacturing, servicing and operating with unmixed fluids, such as material of membrane, dimension of membrane and operating conditions (different season and indoor air quantity needed). For the purpose of reducing energy consumption, a series of experiments have been done to investigate the influence of the main factors affect on the performance of the CFHRV, and the experimental results were analyzed for optimizing the performance of such ventilators by means of mass and heat transfer theory. Moreover, in order to obtain the effectiveness of utilization on the CFHRV, numerical simulations have been carried out for predicting the temperature field and PMV (Predicting Mean Vote) index distributions indoors in the present paper.The experimental data show that the sensible heat effectiveness and moisture effectiveness are both affected by the disposing air quantity under certain conditions. However, the moisture heat effectiveness changes much faster than that of thesensible heat effectiveness when the disposing air quantity varies. At the same time, when the disposing air quantity increases, frictional pressure drop in the membrane increases much more than the empty box. For this reason, when a plate type total heat exchanger was used, the key problem is how to reduce the pressure drop in the membrane. In addition, under a given condition, sensible heat and latent heat effectiveness are affected by the differences of temperature and air moisture between fresh air and return air. Comparing with the sensible heat effectiveness, it has more effect on the moisture effectiveness.The experimental results also shows that longer flow crossing path ensures more sensible heat effectiveness and moisture effectiveness under the same operating conditions. Furthermore, the trend is more obvious as air velocity increases near the surface of membrane, and it has more effect on the moisture effectiveness than sensible heat effectiveness. Thus, the effect of material of the membrane on sensible heat effectiveness is weaker than latent heat effectiveness.Numerical results show that the indoor temperature field and PMV distributions are more homogeneous when a CFHRV was used under the same energy consumption in an air conditioning room. It means that when HRVs are used in the zones where the differences of temperature and air moisture are higher between fresh air and return air is more, the people in rooms should feel more comfortable.