Theoretical investigation of the performance of a novel loop heat pipe solar water heating system for use in Beijing, China

Abstract

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 o C 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. wi -wicks;wp -water pipe between the heat exchanger and storage tank;

Operational performance of a novel heat pump assisted solar façade loop-heat-pipe water heating system

“…Wang et al [22] presented a novel kind of micro-heat pipe array flat plate solar water heater with an annual average system efficiency of 58.29%. Use of a novel LHP for solar heat collection and transportation was recently proposed by Zhao et al [23] and still at the research stage. Recent research indicated that LHPs used in the buildings' hot water systems could achieve the enhanced performance if the solar absorber and heat exchanger are adequately selected and coupled [23,24].…”

Experimental Study on a Forced-Circulation Loop Thermosiphon Solar Water Heating System

“…Although the volume filling ratio in this study used the previous optimal result, the existence of the pump, condensation liquid storage tank, and evaporation liquid storage tank made the actual evaporation liquid level higher than Zhao et al [25] under the same filling ratio; since the condensation liquid storage tank and evaporation liquid storage tank contribute a big amount of volume; however, those parts had limited contributions on the overall heat transfer.…”

“…According to Zhao et al [25], the loop thermosiphon has the best filling ratio that lies between 30%~50% of the whole volume and has a negative performance when overcharged. …”

“…Some studies using LT on the BIPV/T system are also presented. Zhao et al [25] theoretically investigated the performance of an LT-SWH for a typical apartment building in Beijing.…”

Simulation of Hybrid Photovoltaic Solar Assisted Loop Heat Pipe/Heat Pump System

“…The LHP is a two-phase heat-transfer measure with the working fluid circulating in a loop, thus enabling remote and passive heat transfer at enhanced capacity. Due to its simple operation and environmental effect, LHP has been widely used in the thermal control of satellites and electronics [12][13][14] and it has gradually been gaining attention in the field of solar energy collection and transportation [15][16][17]. The LHP mode is passive, which means it does not consume work.…”