A mechanical and experimental study on the heat loss of solar evacuated tube

The experimental system of heat loss of all-glass evacuated solar collector tubes (evacuated tube) is firstly designed and constructed, which uses electric heater as thermal resource. The equilibrium temperatures are less than ±1°C during the test, and the temperature differences of up/middle/low node in the tube are less than 1°C, 3°C, and 7°C respectively. The heat loss of evacuated tube increases about 2.7% with vacuum state of 0.01–1 mPa, and it has the best performance at tube temperature of 20–280°C. The invalidation tube (> 200 mPa) has the biggest heat loss that increases linearly with the tube temperature. The evacuated tubes with the vacuum of 0.01–1 mPa are suitable for most solar adsorption refrigeration.