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The heat recovery by the heat pipe heat exchangers was studied in the tropics. Heat pipe heat exchangers with two, four, six, and eight numbers of rows were examined for this purpose. The coil face velocity was set at 2 m/s and the temperature of return air was kept at 24?C in this study. The performance of the heat pipe heat exchangers was recorded during the one week of operation (168 hours) to examine the performance data. Then, the collected data from the one week of operation were used to estimate the amount of energy recovered by the heat pipe heat exchangers annually. The effect of the inside design temperature and the coil face velocity on the energy recovery for a typical heat pipe heat exchanger was also investigated. In addition, heat pipe heat exchangers were simulated based on the effectiveness-NTU method, and their theoretical values for the thermal performance were compared with the experimental results.

The energy conservation potential of the heat pipe based heat exchangers (HPHXs) was studied in this research. To this end, a typical climate chamber as the representative of an air conditioning system was established. The performance characteristic of a typical eight-row HPHX was obtained based on the one week operation (168 h) to determine the performance characteristic curves. The coil face velocity and inside temperature were set at 2 s m / and 24 C o , respectively. Then, the relevant empirical performance equations were used to predict the energy conservation of the HPHX for the years

The effect of heat pipe heat exchanger on the heat recovery was studied in the tropics. The performance of the heat exchanger was monitored during the one week of operation (168 h) to find out the performance characteristic curves. Three coil face velocities namely, 2, 2.2 and 2.5 m/s were tested and the temperature of return air was controlled at 24°C. The relevant empirical equations were then employed for the hour-by-hour prediction of the energy recovery by the heat pipe heat exchanger for the whole year. The impact of inside design temperature on the heat recovery by the heat exchanger was also studied. The thermal performance of the heat pipe heat exchanger was simulated based on the effectiveness-NTU method and the theoretical values were compared with the experimental data. Practical application: Performance improvement of the heating, ventilating and air conditioning systems is a challenge to the designers. The results obtained from this research work could serve as a practical guide for engineers who are intending to use heat pipe heat exchangers in the heating, ventilation and air conditioning systems operating in tropical climates. Engineers and researchers have the potential to use the recommended empirical performance equations to examine the impact of heat pipe heat exchangers on the performance of the current air conditioning systems. Moreover, these empirical performance equations enable the year-round operating effect of heat pipe heat exchangers on energy savings to be predicted realistically.

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An investigation was carried out to study the effect of an air-to-air heat pipe heat exchanger on the energy recovery and dehumidification enhancement of the air conditioning system in tropical climates. For this purpose, the performance of a heat pipe heat exchanger, which was experiencing tropical ambient air in its evaporator section and fan coil unit, was monitored during one week of operation (168 hours) to find out the relevant performance characteristic curves. Then, empirical equations, which were extracted from the performance characteristic curves, were employed for the hour-by-hour prediction of energy recovery by the heat pipe heat exchanger and dehumidification for the whole year using TRNSYS software. The investigation showed that the heat pipe heat exchanger can pay for itself in 1.9 years. Moreover, it was shown that the dehumidification capability of the cooling coil can enhance up to 6% with the added heat pipe heat exchanger.