Thermal analysis of a plastic helical coil heat exchanger for a domestic water storage tank

In the present study, the heat transfer coefficients of helically coiled corrugated plastic tube heat exchanger inside of the solar boiler vessel were investigated experimentally. The metal coil of the conventional solar boiler for domestic usage was replaced by a plastic tube and the results were compared with the numerical simulation and the technical documentation of the initial solar boiler. All the required parameters like inlet and outlet temperatures of tubeside and stratified temperatures, flow rate of fluids, etc. were measured using appropriate instruments. The test runs were performed for different temperatures inside the tank ranging from 30-60°C and different flow rates from which the heat transfer coefficients were calculated

Charging of a thermal battery composed of open-cell metal foam and phase change material for use in pharmaceuticals transport

Active coolers for pharmaceutical transport require maintenance significantly and present risks with movable parts. Passive coolers on the other hand have less components and do not require chilling units on board unlike their active counterparts. Phase change materials (PCM) have already been used in pharmaceutical logistics for the constant temperature provided thanks to the latent heat released during melting. However, before docking the gel packs require a significant amount of time for freezing due to their low thermal conductivities. In this study, the overall thermal conductivity of the enclosures of PCMs in a thermal battery is increased via combining them with open-cell metal foams. Experimental results on the thermal battery prototype show that the attempts for quickening the freezing process are promising for further research.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

Parametric study of a triangular cross corrugated plate

The main goal of this study is to investigate the influence of apex angle and Reynolds number on the thermal hydraulic performance of triangular cross corrugated plates. More specifically this work focuses on triangular cross corrugated plate with the orientation angle of 90°. The computational fluid dynamics (CFD) method is used to conduct, three-dimensional simulations for 426 < Re < 2021 in a periodic unitary cell. The Reynolds Stress model is used as the turbulence model. The numerical results are in a very good agreement with experimental results correlation. They show deviations between 0.8 – 4.84 %. The highest thermal performances are achieved by the both apex angle of 120° and 90°. The lowest thermal performance is observed by the apex angle of 55°. The heat exchanger with the apex angle of 90° has the highest friction factor. For the Reynolds number lower than 1300, the apex angle of 120° shows the lowest friction factor. However for the Reynolds number higher than 1300, the apex angle of 55° shows the highest hydraulic performance.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

Charging of a thermal battery composed of open-cell metal foam and phase change material for use in pharmaceuticals transport

Active coolers for pharmaceutical transport require maintenance significantly and present risks with movable parts. Passive coolers on the other hand have less components and do not require chilling units on board unlike their active counterparts. Phase change materials (PCM) have already been used in pharmaceutical logistics for the constant temperature provided thanks to the latent heat released during melting. However, before docking the gel packs require a significant amount of time for freezing due to their low thermal conductivities. In this study, the overall thermal conductivity of the enclosures of PCMs in a thermal battery is increased via combining them with open-cell metal foams. Experimental results on the thermal battery prototype show that the attempts for quickening the freezing process are promising for further research.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

Two-phase heat transfer measurements of R254fa at high saturation temperatures in horizontal mini-channels

Heat transfer measurements for R254fa were conducted. The heat transfer coefficient was determined for a smooth stainless steel tube with an inner tube diameter of 3 mm. The experiments were conducted for five mass fluxes (100, 300, 500, 700 and 1000 kg/(m².s)), three heat fluxes (10, 30 and 50W/m²) and at three saturation temperatures (40°C, 70°C and 125°C). The experiments were used to determine the influence of the saturation temperature, mass flux, heat flux and vapour quality on the heat transfer coefficient. At a low saturation temperature, the heat transfer coefficient increases with an increasing mass flux. However, at a high saturation temperature the heat transfer coefficient decreases with an increasing mass flux. Furthermore, the heat transfer coefficient increases with increasing vapour quality at a low saturation temperature. On the contrary, the heat transfer coefficient decreases at higher saturation temperatures

Feasibility study of a plastic helical coil heat exchanger for a domestic storage tank

The main goal of this study is to investigate whether it is possible to use a polymeric helical coil heat exchanger as an alternative to conventional metallic helical coil. More specifically this work focuses on a helical coil design for a domestic water storage tank application. Corrosion and fouling resistance, scarcity of the materials, low weight and cost are the driving forces to consider designing polymeric heat exchangers rather than metallic heat exchangers. However, simply replacing the metallic material by the polymer material and applying the traditional design methods used for metallic heat exchangers do not lead to an acceptable design. If one wants to design a good polymer heat exchanger, heat transfer and structural problems have to be solved first. In addition, the pressure drop limitation should not be neglected. In order to reach this goal, a model is developed to predict the optimal design of a helical coil heat exchanger immersed in the water storage tank for a certain water mass flow rate and temperature. This design compensates for the low thermal conductivity and strength of the polymer