Abstract Pulsating heat pipes (PHPs) represent a contemporary and highly efficient thermal technology that utilizes the oscillatory motion of a fluid within capillary tubes to facilitate heat transfer from the evaporator (heat source) to the condenser (heat sink), negating the necessity for moving mechanical components. In this work, a comprehensive experimental study of the thermal performance of a PHP heat exchanger (PHPHE) is conducted, designed to recover waste energy in air conditioning systems and exchange heat between two air streams in a counterflow configuration. The system consists of six rows of pulsating heat pipes (PHPs), each containing six turns, divided into three main sections: evaporator, adiabatic section, and condenser, with lengths of 25, 10, and 25 cm, respectively. The novelty of this study lies in applying a multiple pulsating heat pipe heat exchanger (PHPHE) with pure water, methanol, and acetone as the working fluid for air-conditioning systems, which were utilized at three different fill ratios of 50%, 60%, and 70%. The study examines how using it as a working fluid in PHPHE affects HVAC system performance. Tests were carried out using three air flow velocities (0.5, 0.7, and 0.9 m/s) and three evaporator air inlet temperatures (40 °C, 45 °C, and 50 °C) to investigate their effect on the performance of the PHPHE. Results indicated that raising the inlet air temperature to the evaporator has a positive impact on the heat transfer rate. Results indicated that raising the inlet air temperature to the evaporator has a positive impact on the heat transfer rate. At a filling ratio of 50%, the thermal performance of the pulsating heat pipe was consistently superior, attaining the best balance between fluid flow and volume compared to 60% and 70%. The enhancement ranged between 5.2% and 28.6% for acetone, 5.1% to 26.3% for methanol, and 4.1% to 30.3% for water, confirming that a 50% filling ratio provides the most effective operation. Furthermore, acetone demonstrates superior effectiveness compared to methanol and water, achieving 32% effectiveness at a 50% fill ratio under suitable operating conditions. The overall system effectiveness for the three liquids ranged from a minimum of 15% for water to a maximum of 32% for acetone.
Moayad et al. (Sat,) studied this question.