Effect of baffle plate on the performance of a triangular built-in-storage solar water heater

Abstract

The triangular design of a solar water heater not only enhances the overall gain to the system but also improves the natural convection between the absorbing plate and the water, leading to better performance of the system. A night insulation cover is used at the top surface of the heater to reduce the losses from the system during the off-sunshine hours. Another way to reduce the losses from the system is by using an insulating baffle plate in the tank. This plate divides the tank water into two portions, the water above this plate is known as the upper column and below is known as the lower column. The water of the two columns is in contact with each other with the help of the incoming and outgoing vents provided in the baffle plate. This plate also suppresses losses from the lower column during the off-sunshine hours. In this paper, we have studied the effect of a baffle plate on the performance of a triangular built-in-storage solar water heater. To obtain the thermal behavior of the system, the energy balance equations are written at the different nodes, and the well-known finite difference forward time step marching technique is used for their solution. The proposed system is studied by varying the vent area, the water mass in the two columns and under a constant flow rate for different durations. The effects of the thermal conductivity and thickness of the baffle plate on the water temperature are also investigated. It is found that the presence of the baffle plate greatly improves the system performance during off-sunshine hours.