Experimental Analysis of a Bayonet Tube at Constant Wall Temperature Conditions Under Laminar, Transition, and Turbulent Flow

An experiment was carried out on a bayonet tube that was kept at a constant temperature using condensing steam. In contrast, cold water was permitted to enter the central tube and discharge via an annular portion. The water flow rate was varied, covering laminar, transition, and turbulent regimes. The inner part of the bayonet tube is CPVC (chlorinated polyvinyl chloride, k = 0.136 W · m⁻¹ · K⁻¹), which reduces short-circuit heat transfer across the tube. Temperatures were recorded at different points in the tube. From the results of experiments on total heat transfer and short-circuit heat transfer, the Nusselt number can be calculated. The pressure drop across a bayonet tube determined the friction factor. In examining a range of Reynolds numbers, Effectiveness and figure of merit have been resolved. It has been observed that as the Reynolds number increases, the Nusselt number increases while the friction factor decreases. Both Effectiveness and Figure of Merit decrease with the addition of the Reynolds number, and it is observed that the maximum effective value is 0.86 for a 75 Reynolds number, which is suitable for bayonet solar collectors, and the minimum effective value is 0.2 for an 8062 Reynolds number, which is suitable for bayonet heat exchangers. It serves as reference work for bayonet tubes for designing a parabolic solar collector and heat exchanger.