Estudio del proceso de ebullición en el interior de un tubo multipuerto extruido en aluminio con mini-canales de geometría triangular usando R32 y R134A como fluidos de trabajo

Abstract

The use of multiport mini-channel tubes in compact exchangers has increased in the last few years. They contributing to improve thermal efficient, compactness, energy conservation and required lower refrigerants charge by which reduction of greenhouse gases emission. Those mentioned advantages are very important aspects with regard to modern refrigeration systems design. For that reason, several experimental investigation have been carried out in order to characterize the flow boiling heat transfer process and frictional pressure drop in tubes with parallel channels. Since, the ability to estimate pressure drop and heat transfer coefficient for specific conditions is a fundamental issue to optimise the design of compact heat exchanger. In this study, the characteristics of two- phase flow pressure drop and convective boiling heat transfer have been investigated experimentally inside multiport mini-channel aluminium tube with triangular geometry, hydraulic diameter 0.715 mm and heating length of 1205 mm using R32 and R134a as working fluids. A wide experimental campaign has been carried out to complete an array of measurement under different conditions for both refrigerants studied. The experimental conditions examined included: mass velocity 275-1230 kgm-2s-1, heat flux 0.75-9.30 kWm-2, saturation temperature, 5°C, 7.5°C, 12.5°C, vapour quality 0.012-0.51. The database presented consists of 312 averages values, 223 averages values were recorded for R134a and 89 for R32. The flow boiling averages values were calculated selecting a sample of 40 readings (steps 20s) in stable conditions for all measured variables at each mass velocity tested.