Mathematical Modeling and Thermal Analysis of Evacuated Flat Plate Collector in Pakistan

Energy is a key parameter for a country's development. From recent decades Pakistan is facing energy crises due to the limitation of traditional energy resources. In Pakistan, natural gas, electricity, and coal are used for domestic hot water systems and industrial process heat. Due to climate change, traditional energy resources are declining, and energy demand is increasing. To support the developmental work, increasing population, and industries, Pakistan will need energy in an abundant amount to run the system on the proper track. To solve these problems, we just need to replace traditional energy resources with renewable energy. Solar thermal collectors are sources to complete the demand for hot water on small and large scales. This paper demonstrates an evacuated flat plate collector having an area of 4 m2 and working fluid water-glycol mixture inside the tubes circulates with different mass flow rates of 0.01 to 0.1 kg/s with the help of a pump. The vacuum is created inside the collector with the help of a vacuum pump and pressure maintained less than 1 bar. Program is generated in MATLAB and simulated under design conditions of the collector with input weather data collected from meteorological high precision equipment installed at US-PCASE, NUST Islamabad, Pakistan having a latitude of 33.64° N and longitude of 72.99° E. By evacuating the enclosure convective losses from plate to cover are drastically reduced, which in turn decreases overall heat loss coefficient from 7.50 to 4.60 W/m2K. absorber temperature is also increased due to reduction of convective losses, which in turn increases fluid outlet temperature by 7 to 9 °C and also increases the efficiency of the collector by 7 % as compared to non-evacuated flat plate collectors.