Issues of Development of Solar Collectors with High Efficiency

The article deals with the creation of energy-efficient solar water collectors. In order to develop energy-efficient solar water collectors (SWC), methods of rational enhancement of heat transfer in the channels of the collectors are proposed. It is noted that the methods used to increase heat transfer from the collector walls to the water should be tailored to a low-speed flow of the heat carrier. With such flow regimes, the most acceptable ways to enhance heat transfer are: flow swirling, the use of artificial roughness, renewal of the hydrodynamic boundary layer through the creation of an alternating pressure gradient in the flow. The analysis of the conducted research shows that the maximum effects of increasing heat transfer occur in the range of Re numbers from 2000 to 8000, i. e. in the laminar flow region and in the region of underdeveloped turbulence. An efficiency criterion is obtained for the conditions under which enhancers are installed inside the pipes. The criterion determines the ratio of the number of pipes with enhancers to the number of smooth pipes. The calculation is carried out for cases in which the heating capacity, flow rate, power for heat carrier circulation and the pipe diameter of the SWC with smooth pipes are equal to the heating capacity, flow rate, power for heat carrier circulation and pipe diameter of the SWC with the pipes with enhancers. In addition to the specified efficiency criterion of the SWC, a heat transfer comparison formula of the SWC having pipes with enhancers and SWC with smooth pipes is obtained