This paper presents a comparative study of the cross-flow regenerative heat and mass exchanger (HMX) and the conventional cross-flow HMX for indirect evaporative cooling (IEC) with numerical methods. The objective of this study is mainly to clarify the applicability of the two HMXs. The numerical model was built and validated by existing experimental data. The difference in heat and mass transfer between the two HMXs was revealed by analyzing the change of the temperature and moisture content of the air, and the influence of the main operating parameters on the cooling performance of the HMXs was analyzed. In the typical operating conditions, when the HMXs are used alone, the cooling performance of the regenerative HMX is better than that of the conventional HMX under low supply air flow rate. When the HMXs are used in the multistage evaporative cooling systems with high supply air flow rate, the conventional HMX is more suitable as the first stage of the system to pre-cool the supply air, while the regenerative HMX is more suitable as the second stage to re-cool the supply air.

In the age of the digital economy, the data center is the most crucial piece of infrastructure. The issue of the excessive power consumption of a data center’s cooling system needs to be addressed as the national objective of “peak carbon and carbon neutrality” is increasingly promoted. In this study, a microchannel-separated heat pipe-cooling system with evaporative condensation is introduced. The system may switch between three modes of operation in response to changes in outdoor air quality parameters, thereby maximizing the utilization of natural cooling sources while lowering data centers’ cooling costs. The purpose of this paper is to analyze the energy-saving potential of the hybrid system through experimental tests. The results show that 114.4% is the ideal liquid-loading rate for the heat pipe system. Under working conditions in Xi’an, the annual operating hours of the three modes accounted for 47.2%, 6.1%, and 46.7%. The hybrid cooling system may save 62.04% of the energy used annually compared to the standard cooling system and the cooling system in the server room thanks to its yearly average COP of 9.43.

A new evaporative condensation refrigerant pump heat pipe air-conditioning unit based on a microchannel heat pipe heat exchanger is proposed. Performance experiments were conducted on the unit, and the experimental results show that the cooling capacity of the unit in the dry, wet, and mixed modes can reach 112.1, 105.8, and 115.4 kW, respectively, the optimal airflow ratio of the secondary/primary airflow is 2.2, 1.8, and 1.8, respectively, and the EER decreases with increasing airflow ratio. With increasing dry- and wet-bulb temperatures of the secondary-side inlet air, the cooling capacity and energy efficiency ratio of the unit decrease, and the energy efficiency ratio in the wet mode is higher than that in the dry mode, which can prolong the operating hours of the wet mode within the operating temperature range of the dry mode and improve the energy efficiency of the unit. A new calculation method for the refrigerant charge is proposed, and the optimal refrigerant charge is 32 kg based on the experimental results, which agrees with the theoretical calculation results.

In order to solve the easily scalable problem of evaporative condensing equipment, re-search was conducted on the development of a new type of self-priming scaling evaporative condenser with a built-in electrochemical scale absorber which changes the traditional water quality treatment cycle method from “preventing scaling” to “self-priming scaling”, integrating treatment devices and an evaporative condenser in order to realize the integration and modularization of the equipment. Experimental results show that the new self-priming scaling evaporative condenser has a condensing temperature range of 36.7~38.9 °C, heat rejection range of 716.69~768.66 kW, and, under different load rates, a condensing temperature range of 22.7~36.7 °C. The new self-priming scaling evaporative condenser system’s energy efficiency ratio COP has a range of 3.26~3.44. The coefficient of performance IPLV is 3.9, which exceeds the design index value. After the unit ECT electrochemistry meter is turned on, it effectively reduces the concentration multiplier of water quality: the total hardness increase per minute is reduced from 0.4 mg/L to 0.23 mg/L, a reduction of 42.5%. Turning on the electrochemistry meter also effectively reduces the increase in the total hardness and reduces the occurrence of scaling in the evaporative condenser unit.