Heat Transfer and Fluid Flow Over A Bank of Longitudinally Finned Flat Tubes: A Numerical Study

This computational study investigates the heat transfer rate and fluid flow characteristics of a staggered arrangement of longitudinally finned flat tube banks ( ) with a constant surface temperature. The finite volume method ( ) is used to solve the governing equations using the commercial software . This study considers longitudinal pitch ratios ( ). In addition, the dimensionless transverse pitch ratio ( )=3 and both the dimensionless upstream fin length ratio ( )= ( ) =0.8 is the dimensionless fin angle . The focus of the investigation is a Reynolds number range between  with constant physical properties. The analysis examines pressure drop, dimensionless heat transfer rate, and the average Nusselt number. Results indicate that as Reynolds numbers increase and dimensionless longitudinal pitch ratios decrease, the heat transfer rate between tube surfaces and airflow increases to reach maximum value of 275. In addition, the Reynolds number affects the pressure drop, Began number, average Nusselt number, and thermal hydraulic performance

Aheat transfer and fluid flow characteristics in a TBHE based on constructal design : An overview

With the beginning of the industrial revolution in the eighteenth century, ICE, refrigeration equipment and power stations developed. All of the above devices use TBHE. The important thing is the recent increase in energy demand, which led researchers to find optimal solutions to save the largest amount of energy. The objective of this review can be summarized in the research published in the field of TBHE of all kinds. In order to improve the performance of the TBHE, two basic conditions must be met, the first is to increase the CHTC, and the second is to reduce the PD across the HE. In order to reach this goal, many influential variables must be studied, including pipe diameters and shapes, vertical and horizontal distances, fins shape, and installation method. In addition to the arrangement of the tubes through the TBHE. It was in the form of IL or staggered, the type of flow that was stratified or turbulent. The most important variables affecting on the performance of HEs can be summarized in general. The shape of the pipes had a greater urgency in the process, as the flat pipes had better performance than the circular TBHE. Both the PD and the CHTC are a function of the Reynolds number, as both increase with the increase in the Reynolds number. Therefore, studies in this field must be intensified to obtain the optimal design TBHE, taking into account all the above variables

Theoretical and Experimental Investigation of Forced Convection of Airflow Over Longitudinally Finned Flat Tube Bank Heat Exchanger

Heat exchangers play a crucial role in various industrial applications. The present paper numerically and experimentally investigated the effects of the Reynolds number (Re), dimensionless transverse pitch ((S_T ) ̂), dimensionless longitudinal pitch ((S_L ) ̂), dimensionless upstream fin length ((L_u)) ̂, dimensionless downstream fin length ((L_d ) ̂), and dimensionless fin angle (θ ̂) on the heat transfer performance of a longitudinally finned flat tube bank heat exchanger (LFFTBHE) with staggered configurations. The constant surface temperature was assumed. The studied parameters ranges were 223≤Re≤1114, 3≤(S_T ) ̂≤5, 4≤(S_L ) ̂  ≤ 5, 0.4≤(L_u ) ̂≤ 1, 0.4≤(L_d ) ̂≤1.0, and 0.26≤θ ̂≤ 0.78. The results showed that the average Nu increased steadily with Re, i.e., 6.3≤Nu≤14.6. Nu reduced up to 18% with increasing (S_T ) ̂. Nu slightly improved with increasing (S_L ) ̂ up to 2.1%. Nu decreased with increasing (L_u ) ̂ up to 12%. (L_d ) ̂ showed a contradictory impact on Nu depending on Re. θ ̂ increase improved Nu up to 15.5%. Two correlations were proposed based on the numerical and experimental data

A review of phase change heat transfer in shape-stabilized phase change materials (ss-PCMs) based on porous supports for thermal energy storage

Latent heat thermal energy storage (LHTES) uses phase change materials (PCMs) to store and release heat, and can effectively address the mismatch between energy supply and demand. However, it suffers from low thermal conductivity and the leakage problem. One of the solutions is integrating porous supports and PCMs to fabricate shape-stabilized phase change materials (ss-PCMs). The phase change heat transfer in porous ss-PCMs is of fundamental importance for determining thermal-fluidic behaviours and evaluating LHTES system performance. This paper reviews the recent experimental and numerical investigations on phase change heat transfer in porous ss-PCMs. Materials, methods, apparatuses and significant outcomes are included in the section of experimental studies and it is found that paraffin and metal foam are the most used PCM and porous support respectively in the current researches. Numerical advances are reviewed from the aspect of different simulation methods. Compared to representative elementary volume (REV)-scale simulation, the pore-scale simulation can provide extra flow and heat transfer characteristics in pores, exhibiting great potential for the simulation of mesoporous, microporous and hierarchical porous materials. Moreover, there exists a research gap between phase change heat transfer and material preparation. Finally, this review outlooks the future research topics of phase change heat transfer in porous ss-PCMs

Thermal Energy Storage for Solar Energy Applications Based on Regular and Composite Nano-Phase Change Materials

The fluctuating behavior of thermal solar energy creates an enormous need to store thermal solar energy during available periods and use it when unavailable. Among different thermal energy storage techniques, latent thermal energy storage using phase change materials or PCMs has many attractive characteristics, e.g. a low ratio of volume to energy, and isothermal charging and discharging processes. However, the thermal behavior of most phase change materials is alleviated by their low thermal conductivity. To study the potential enhancement of the performance of latent thermal energy storage, dispersing metallic nanoparticles and using metal foams were investigated in the present work. Rectangular and square thermal storage units were studied both experimentally and numerically. Furthermore, a scale analysis of the melting process was performed. In addition, energy streamlines and heatline calculations were performed. Finally, exergy analyses were performed for closed latent heat storage. The numerical model used in the porous case was the Brinkman model. The experimental and numerical results showed that the metal foam significantly enhanced the thermal behavior of the thermal storage unit when compared with the nanoparticles. In order to improve the nano-PCM thermal behavior, more nanoparticles should be used. Nevertheless, using high volume fractions of nanoparticles caused sedimentation.Ministry of Higher Education and Scientific Research of Ira

Thermal performance of novel indirect passive solar dryer

An experimental investigation was conducted to study the performance of a novel indirect type free convection solar dryer. The novel and a conventional indirect passive solar dryer were built. Solar irradiation and temperature of different locations were recorded. The air at the drying chamber entrance, lower space, and upper space temperatures besides the thermal efficiency of the novel dryer were 68, 39, 49 and 85%, respectively, higher than the conventional one

Experimental Investigation in Cross-Flow Heat Transfer of Air Over LFFTBHE

The heat transfer and fluid flow of airflow in a staggered flat tube bank in crossflow with laminar forced convection are experimentally investigated and presented in this study. Two rows of finned tubes were placed perpendicular to the flow direction. The air velocity varies between 0.29 m/s–1.46 m/s, and the Reynolds number approximately ranged from . The surface temperature in all tubes is constant. The dimensionless upstream fin length ( =0.4, 0.6, 0.8, and 1), respectively, and the dimensionless downstream fin length( the dimensionless transverse pitch ( ) of 3.0, the dimensionless longitudinal pitch ( ) =4.0, and the dimensionless fin angle ( =0.52 with constant physical properties. The results show that the Nusselt number, friction factor, and Colburn factor are inversely proportional to the upstream fin length. The percentage of deficient was 14%, 12%, and 35%, respectively, in contrast to the Bejan number, where the percentage of improvement was 11%. Correspond to the highest value of the Reynolds number. This is fully consistent with the principles of Constructal Law

Thermal performance of novel indirect passive solar dryer

An experimental investigation was conducted to study the performance of a novel indirect type free convection solar dryer. The novel and a conventional indirect passive solar dryer were built. Solar irradiation and temperature of different locations were recorded. The air at the drying chamber entrance, lower space, and upper space temperatures besides the thermal efficiency of the novel dryer were 68, 39, 49 and 85%, respectively, higher than the conventional one.</jats:p

Experimental Study of Innovative Indirect Solar Dryers

The present work experimentally studied two novel solar dryers’ designs, novel indirect solar dryer (NISD) and novel mixed indirect solar dryer (NMISD). The purpose behind this work is to compare the thermal performance of the proposed dryers with that of a traditional indirect solar dryer (TISD). The testing method involved building and thermally testing the three dryers. The NISD is a novel drying chamber with three absorbed surfaces. The NMISD consisted of a flat plate solar collector and NISD. The air temperature at the drying chamber entrance increased by 60% and 68% for the TISD and NMISD, respectively. In the lower space of the drying chamber, the air temperature was decreased by 35% while increased by 39% for the NISD and NMISD, respectively, compared to the TISD. The air temperature in the upper space of the drying chamber increased by 14% and 49% for the NISD and NMISD, respectively, compared to the TISD. The temperature variations through the drying chamber were -26%, 33%, and 3% in the TISD, NISD, and NMISD, respectively. The thermal efficiencies of the NISD and NMISD were 9% and 55%, respectively, higher than the TISD’s.</jats:p