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

Abstract

Wickless gravity loop thermosiphons (LTs) have been widely used in heat collection for distances up to several meters. This twophase closed device, which is operating under reduced pressure, is useful in solar water heating (SWH) systems because it could address the freezing problem during winter. Compared to the normal type, forced-circulation wickless LTs have significant advantages in the long-distance heat transfer and installation freedom of condensation section. In this study, a pump-forced wickless LT-SWH system with a remolded flat-plate solar collector was put forward. Solar collector acted as the evaporation section of the wickless LT, while the spiral heat exchanger in the water tank acted as the condensation section. R600a was employed as the working fluid, and long-term outdoor experiments were carried out. Results show that the instantaneous and daily average photothermal efficiency of the proposed system can reach 69.54% and 58.22%, respectively. Temperature differences between the top and bottom and the middle and bottom of the evaporation section of the wickless LT were small, and it usually ranged between 1.1 and 3.9°C. Linear fittings of the collector and system overall performance of the pump-forced wickless LT-SWH system demonstrate the promising potential application of the system.

Experimental investigation and annual performance mathematical-prediction on a novel LT-PV/T system using spiral-descent concentric copper tube heat exchanger as the condenser for large-scale application

“…PV/LHP/solar assisted heat pump water heating system [13] R22 53% Daily thermal efficiency in transition seasons, summer and winter: 53.64%, 52.63% and 47.84% Pump-forced wickless LT-SWH system [30] R600a 0 Typical thermal efficiency:…”

Multi-thermal performance optimization of semi-circular heat pipes integrated with various solar collector profiles

“…7a-c. The TE of the HP is computed by the proportion of heat rejected at the condensing region to heat inlet at the vaporizing region (Zhang 2018). The effect of A, B, and C on TE showed a gradual decrease with the increase of A initially and then increases with increasing C producing a sudden overall increase in TE.…”

A review of thermal interface material fabrication method toward enhancing heat dissipation

“…Some works concentrated on the simulation design as pre‐fabrication to optimize the design and predicted the good output performance 19‐21 . Thermosiphon is also an alternative on heat exchanger and heat pipe cooling system where the hot and cold air will be directed based on density difference and produce natural convection 22,23 . It is applied in the solar energy system, replace for water coolant or thermoelectric cooling such as TEC (as shown in Figure 3 when coupled to CPU) 24,25 …”

“…[19][20][21] Thermosiphon is also an alternative on heat exchanger and heat pipe cooling system where the hot and cold air will be directed based on density difference and produce natural convection. 22,23 It is applied in the solar energy system, replace for water coolant or thermoelectric cooling such as TEC (as shown in Figure 3 when coupled to CPU). 24,25 The conventional heat exchanger technologies consist of transferring heat from a hotspot location in a device to a fluid medium such as air or liquid coolant through a tube.…”