Heat Transfer Coefficient Of Copper Block Mini-Channel Evaporators Used For Vaccine Delivery Boxes

Proper storage of the vaccines and drugs is one of the top priorities in the world of medical practice.Storage at high temperature can quickly degrade the potency and stability of many medicines.The need to have at least a miniature refrigeration system is essential for proper storing and for transport of temperature-sensitive vaccines and drugs especially in rural areas in the Philippines where power supply is normally a problem.This study aims to design, fabricate, and evaluate the heat transfer coefficient of copper block mini-channel evaporator used for vaccine delivery boxes.Three (3) 70.0mm x 45.0mm x 7.0mm copper block evaporators with hydraulic diameters of 3.0mm, 2.0mm, and 1.0mm were designed, fabricated, and tested.The units were connected in a small vapor compression refrigeration system using refrigerant R134a as the cooling medium.In the controlled main line, the evaporator temperature showed the same flow characteristic to that of the larger hydraulic diameter of the evaporator tube and a significant reduction in temperature.The result showed that the 3.0mm hydraulic diameter mini-channel evaporator produces the lowest surface temperature of -6.8 o C with heat transfer coefficient of 100.1 W/m 2 -K.The 2.0mm mini-channel evaporator produces -4.9 o C and a heat transfer coefficient of 38.5 W/m 2 -K.The 1.0mm hydraulic diameter mini-channel has the highest evaporator temperature and pressure with a very low heat transfer coefficient.This is caused by the capillary effect on the flow of the refrigerant on the 1.0mm hydraulic diameter tube.