Theoretical Investigation of the Performance of a Novel Loop Heat Pipe Solar Water Heating System for Use in Beijing, China

Xudong Zhao (1) , Zhangyuan Wang (2) , Qi Tang (2)

1 DMU - De Montfort University [Leicester, United Kingdom]
2 Department of the Built Environment

A novel loop heat pipe (LHP) solar water heating system for typical apartment buildings in Beijing was designed to enable effective collection of solar heat, distance transport, and efficient conversion of solar heat into hot water. Taking consideration of the heat balances occurring in various parts of the loop, such as the solar absorber, heat pipe loop, heat exchanger and storage tank, a computer model was developed to investigate the thermal performance of the system. With the specified system structure, the efficiency of the solar system was found to be a function of its operational characteristics - working temperature of the loop heat pipe, water flow rate across the heat exchanger, and external parameters, including ambient temperature, temperature of water across the exchanger and solar radiation. The relationship between the efficiency of the system and these parameters was established, analysed and discussed in detail. The study suggested that the loop heat pipe should be operated at around 72 oC and the water across the heat exchanger should be maintained at 5.1 l/min. Any variation in system structure, i.e., glazing cover and height difference between the absorber and heat exchanger, would lead to different system performance. The glazing covers could be made using either borosilicate or polycarbonate, but borosilicate is to be preferred as it performs better and achieves higher efficiency at higher temperature operation. The height difference between the absorber and heat exchanger in the design was 1.9 m which is an adequate distance causing no constraint to heat pipe heat transfer. These simulation results were validated with the primary testing results.

Mots clés: Loop; Heat Pipe; Solar Radiation; Heat Exchanger; Hot Water; Heating

Domaines: Thermique [physics.class-ph]; Thermique [physics.class-ph]

Xudong Zhao, Zhangyuan Wang, Qi Tang. Theoretical Investigation of the Performance of a Novel Loop Heat Pipe Solar Water Heating System for Use in Beijing, China. Applied Thermal Engineering, 2010, 30 (16), pp.2526. ⟨10.1016/j.applthermaleng.2010.07.002⟩. ⟨hal-00675407⟩