Heat Transfer Analysis and Performance Characterization of a Thermosyphon Flat-Plate Solar Collector for Domestic Water Heating in Kaduna, Nigeria

This study presents an experimental heat transfer analysis and performance characterization of a thermosyphon flat-plate solar water heating system for domestic application in Kaduna, Nigeria (10.5° N, 7.5° E). The research evaluated solar radiation potential, temperature distribution, heat transfer mechanisms, and system performance using a 2.2 m² collector with selective black chrome coating (α ≈ 0.92, ε ≈ 0.12), 250-liter insulated storage tank, and water as working fluid. Experimental measurements were conducted over ten clear-sky days (22nd May to 4th June 2024) using a pyranometer and K-type thermocouples. Results showed peak irradiance of 832 W/m² (average 579.8 W/m²), outlet temperatures exceeding 90°C, and average temperature rise of 30°C across the collector. The overall heat loss coefficient was determined as 6.67 W/m²·K, with transitional flow regime (Re ≈ 2230). The Hottel-Whillier-Bliss efficiency equation was derived as η = 0.78 – 5.20 × [(Ti – Ta)/Gt] (R² = 0.89), with heat removal factor FR = 0.78. Average daily energy output was 16.4 MJ (4.56 kWh), sufficient to heat 150 liters of water from 25°C to 51°C, meeting the hot water requirements of a five-person household. This study provides the first experimentally validated performance characterization of a flat-plate solar collector for domestic water heating in Kaduna, establishing baseline data for system design and policy development in northern Nigeria's solar energy sector.