Experimental study on the thermal characteristics of micro channel separate heat pipe respect to different filling ratio

A micro channel separate heat pipe (MCSHP) that can use natural cold energy was developed to reduce the cooling energy consumptions of telecommunications stations (TSs). Experimental investigations of exploring the optimal refrigerant filling ratio of MCSHP under different outdoor conditions and flow rates were presented. R22 was used as the working fluid. Various refrigerant filling ratios were tested in an enthalpy difference laboratory (EDL) in order to determine the optimal thermal performance for the exterior space temperature range from 8 °C to 23 °C and the air volume flow rate range from 1712 m³/h to 2980 m³/h. In addition, transient and steady-state performance under the optimal refrigerant filling ratio of the MCSHP was studied. As a result of experiments, the optimal refrigerant filling ratio was found in the range from 88% to 101% for different exterior conditions and airflow rates. For the optimal refrigerant filling ratio, the startup time was about 1100 s and then the refrigerant pressures entered a steady state. The cooling capacity and energy efficiency ratio (EER) increased with increasing temperature difference between the indoor and the outdoor; these values were high to 7440 W and 23, respectively, at temperature difference 20 °C. The results are useful for the design and operational control of the MCSHP for TSs.