Effect of the Inlet Aluminum Tube Inner Diameter on the Heat Transfer Performance of Battery Coolers

In this study, based on a two-unit (evaporator and condenser) system bench, the heat transfer performance of a battery cooler with refrigerant-side inlet aluminum tube inner diameters (IATIDs) of 5 mm, 8 mm, 12 mm, and 15 mm was investigated. The effects of the different IATIDs on the pressure drop and heat transfer power of the battery cooler were also investigated. When the IATLD of the battery cooler increased from 5 mm to 8 mm, the pressure drop in working condition 1 (refrigerant side: expansion valve inlet pressure of 2 MPa, valve inlet subcooling degree of 5 ℃, cooler outlet pressure of 0.4 MPa, and cooler outlet superheat degree of 5 ℃, coolant side: inlet temperature of 25 ℃ and flow rate of 16 L/min) reduced from 231.5 kPa to 52 kPa, and the pressure drop in working condition 2(refrigerant side: valve inlet pressure of 1.9 MPa, valve inlet subcooling degree of 5 ℃, cooler outlet pressure of 0.35 MPa, and cooler outlet superheat degree of 5 ℃, coolant side: outlet temperature of 15 ℃ and flow rate of 20 L/min) reduced from 262.5 kPa to 111.7 kPa. The mass flow rate and heat transfer rate increased. When the IATID increased from 8 mm to 15 mm, the pressure drop in working condition 1 reduced from 52 kPa to 13.6 kPa, the pressure drop in working condition 2 reduced from 111.7 kPa to 30.8 kPa, and the mass flow rate and heat transfer rate decreased. The heat transfer rate attained a maximum value at an IATID of 8 mm under the two conditions, i. e. 9214.7 W for condition 1 and 13698.1 W for condition 2. By fitting the relationship between different IATIDs and heat transfer rate, we can match the appropriate IATID to obtain the maximum heat transfer rate.