Analysis of enthalpy change with/without a heat pipe heat exchanger in a tropical air conditioning system

Abstract

SUMMARYIn an earlier paper (Yau, 2006. Application of a heat pipe heat exchanger to dehumidification enhancement in tropical HVAC systems}a baseline performance characteristics study. Int. J. Thermal Sci., accepted for publication), the baseline performance characteristics of the 8-row wickless heat pipe heat exchanger (HPHX) were established for it being used in a vertical configuration under tropical climate conditions. The present paper covers the tests and simulation conducted on the same experimental HVAC system without the HPHX installed, thereby determining the enthalpy change for the air passing through the chilled water coil (CWC) alone (i.e. without the pre-cooling or reheating effect of the HPHX). These experimental results, in comparison with those already obtained, would also allow an examination of how the reheat recovery with the 8-row HPHX installed was influenced by the same key inlet parameters. The final results show that the enthalpy change with a HPHX installed for all cases examined are significantly higher than enthalpy change without a HPHX installed, demonstrating that the cooling capability of the CWC was enhanced by the HPHX.

An experimental and a numerical investigation of HVAC system using thermosyphon heat exchangers for sub-tropical climates

“…Many authors are conducted the application of THEs for HVAC in tropical climates [4][5][6][7][8][9]. They were investigated the energy saving and dehumidification enhancement aspects of different type heat pipe heat exchangers (HPHXs) and made a summary between the experimental and theoretical studies on HPHXs.…”

“…Yau [6,7] investigated the impact of three key factors of entering air state; DBT, RH and air face velocity on the sensible heat ratio (SHR). The experiments and simulations conducted with and without eight rows of THEs in HVAC system.…”

“…It discovers that research on THEs for HVAC reheat and precool process done particularly in the UK, the USA, Australia, and Malaysia [4][5][6][7][8]. Literature surveys moreover detect that only bounded research on THEs for HVAC reheat and precool process was conducted in tropical and no research work on subtropical climates like Middle East.…”

Performance enhancement of an experimental air conditioning system by using TiO2/methanol nanofluid in heat pipe heat exchangers

“…Numerous researches have been reported on experimental and theoretical studies of HPHXs and thermosyphon heat exchangers applied in AC systems. The effects of different operating conditions such as temperature [1][2][3][4][5], relative humidity (RH) [6][7][8], and mass flow rate [9,10] (or velocity [11]) of inlet air as well as mass flow rate ratios [12] of fresh air streams on the performance of HPHX and HVAC systems have been investigated in these studies. In order to overcome problems associated with initiation of boiling process in heat pipes with low temperature differences between inlet and return air streams in AC applications, Wadowski et al [8] designed a heat pipe trigger system.…”

“…Yau [10] carried out experiments to obtain the performance characteristics of a 8-row HPHX with vertical configuration designed for tropical building HVAC systems. By comparing the experimental results with those of a HVAC system without the HPHX installed, it was shown that for all examined cases, the enthalpy changes for the air passing through the chilled water coil (CWC) were considerably higher with the HPHX installed than enthalpy changes without it [9]. Also a series of experiments were conducted in typically high RH conditions on 30°-tilted HPHX in order to enhance drainage of any condensate forming on the fin surfaces of the HPHX evaporator section so that to increase the effectiveness of the HPHX [11].…”