Non-dimensional analysis for heat pipe characteristics in the heat pipe heat exchanger as energy recovery device in the HVAC systems

Abstract

Heat pipe heat exchangers (HPHE) were widely applied as a recovery energy device in HVAC systems and significantly can reduce the energy consumption of HVAC systems. This study performs experimental and non-dimensional analysis using the Buckingham Pi theorem to develop a correlation of heat pipe performance as an energy recovery device in air HVAC systems. The experiment was conducted to investigate heat transfer characteristics in the heat pipe heat exchangers. The fresh-air temperature in the evaporator section (Te,in) was varied at 30–45 °C, fresh air velocity varied at 1.5–2.5 m/s, and the number of rows HPHE varied at 3, 6, and 9 rows. While the return air temperature was entering the condenser's inlet side, HPHE (Tc,in) was kept at 23 °C. The procedures of the Buckingham Pi theorem were adopted to determine non-dimensional parameters and found a correlation between Pi forms. Each non-dimensional parameters value was calculated based on the measured data. The correlation between non-dimensional parameters can be solved simultaneously using the multiple linear regression with the logarithmic transformations method. The new correlation has been found in the form Sp Number. The results show that Sp numbers is affected primarily by the number of rows (n), effectiveness (ε), and Reynold numbers (Re,D). The equation Sp number can be used to predict the thermal resistance of a single heat pipe and is very useful to know the performance of a heat pipe in the design and operating stages.