Experimental investigation of a novel solar air heater based on heat pipe vacuum tube collector integrated with finned-tube heat exchanger

The study intends to analyze the thermal performance of a novel solar air heater based on heat pipe vacuum tube solar collector and finned-tube heat exchanger. The solar collector has been introduced with a new header where heat transfer fluid (Therminol-55) gains heat directly in contact with the condenser section of the heat pipe. This eliminates thermal paste application between the condenser and manifold in the existing systems. The system's thermal performance has been experimentally evaluated using two different (four-row and eight-row) finned-tube heat exchangers at four varied air flow rates, viz. 100 kg h–1, 400 kg h–1, 700 kg h–1 and 1000 kg h–1. The system with eight-row heat exchanger performed better than the four-row heat exchanger at each air flow rate. 100 kg h–1 resulted in a maximum rise in temperature of air (55.4 °C) and maximum outlet temperature of air (89.4 °C). Meanwhile, the maximum energy and exergy efficiency of 95.7% and 2.17% were observed at 1000 kg h–1. The maximum effectiveness of the four and eight-row heat exchangers was found as 70.7% and 79.4%, respectively, at 100 kg h–1. The monthly cost saving by utilization of the proposed system is 65.65 $, and the payback period is 12.4 months. The amount of CO2 averted from releasing into the atmosphere is 787.7 kg per month. The results suggest the utility of the proposed solar air heater as an environment-friendly replacement for conventional air heaters for consistent operation in the daytime. The experimental study was performed at the campus of NIT Kurukshetra, India (29.9476°N, 76.8155°E).