Geometric Parameters Of Heat Exchanger Research Articles

Performance analysis of a K2CO3-based thermochemical energy storage system using a honeycomb structured heat exchanger

The application of thermal energy storage using thermochemical heat storage materials is a promising approach to enhance solar energy utilization in the built environment. Potassium carbonate (K2CO3) is one of the potential candidate materials to efficiently store thermal energy due to its high heat storage capacity and cost-effectiveness. In the present study, a 3-dimensional numerical model is developed for the exothermic hydration reaction of K2CO3. The heat produced from the reaction is transferred indirectly from the thermochemical material (TCM) bed through the walls of the honeycomb heat exchanger to a Heat Transfer Fluid (HTF). A parametric study is conducted for varying geometrical parameters of the honeycomb heat exchanger. The obtained results indicate that the reaction rate and heat transport in the TCM bed strongly depends on the geometrical parameters of the heat exchanger. Reducing the cell size of the honeycomb heat exchanger up to a certain level provides better thermal transport as well as improved reaction rate of the TCM bed. The results of this study provide detailed insight into the heat release processes occurring in a fixed bed of K2CO3. The study is useful for designing and optimizing thermo-chemical energy storage modules for the built environment.

Plate-fin heat exchanger network modeling, design and optimization – a novel and comprehensive algorithm

PurposeThe purpose of this paper is to present a novel and applied method for optimum designing of plate-finned heat exchanger network. Considering the total annual cost as the objective function, a network of plate-finned heat exchanger is designed and optimized.Design/methodology/approachAccurate evaluation of plate-finned heat exchanger networks depends on different fin types with 10 different geometrical parameters of heat exchangers. In this study, fin numbers are considered as the main decision variables and geometrical parameters of fins are considered as the secondary decision variables. The algorithm applies heat transfer and pressure drop coefficients correction method and differential evolution (DE) algorithm to obtain the optimum results. In this paper, optimization and minimization of the total annual cost of heat exchanger network is considered as the objective function.FindingsIn this study, a novel and applied method for optimum designing of plate-finned heat exchanger network is presented. The comprehensive algorithm is applied into a case study and the results are obtained for both counter-flow and cross-flow plate-finned heat exchangers. The total annual cost and total area of the network with counter-flow heat exchangers were 12.5% and 23.27%, respectively, smaller than the corresponding values of the network with cross-flow heat exchanger.Originality/valueIn this paper, a reliable method is used to design, optimize parameters and the economic optimization of heat exchanger network. Taking into account the importance of plate-finned heat exchangers in industrial applications and the complexity in their geometry, the DE methodology is adopted to obtain an optimal geometric configuration. The total annual cost is chosen as the objective function. Applying this technique to a case study illustrates its capability to accurate design plate-finned heat exchangers to improve the objective function of the heat exchanger network from the economic viewpoint with the design of details.

Numerical Study of Heat Transfer Enhancement in Contour Corrugated Channel Using Water and Engine Oil

Improving the design of geometrical parameters of heat exchanger leads to enhance heat transfer and makes it further compacted which in turn increases the efficiency of the thermal process, leading to save operating costs. In the present investigation, thermal and hydraulic performance of laminar flow of the trapezoidal, sinusoidal, and straight counter heat exchanger with water and engine oil was carried out numerically over Reynolds number ranges of 1100-2300 for water and 250 for engine oil. The effect of wave height and wavelength of both trapezoidal and sinusoidal on the thermal properties and hydraulic performance are studied. The numerical study showed that the effect of wave height on the Nusselt number was greater than that of wavelength in both trapezoidal and sinusoidal channels. The study also showed that the trapezoidal channel's influence on Nusselt number was higher than that of the sinusoidal channel and straight channel respectively. Thermal and flow characteristics are explored with the help of the streamwise velocity and isotherms contours for trapezoidal and sinusoidal-corrugated channels. In addition, the success of the heat exchanger design was evaluated by the results of the thermal performance criteria. The results of the thermal performance criteria at all wave heights and wavelength of the corrugated channel were greater than 1, which is indicating that the heat transfer rate is higher than the friction losses. Consequently, the use of corrugated surfaces in Contour heat exchangers can improve heat transfer in many applications.

The Impact of Heat Exchangers’ Constructions on the Melting and Solidification Time of Phase Change Materials

An application of latent heat thermal energy storage systems with phase change materials seems to be unavoidable in the present world. The latent heat thermal energy storage systems allow for storing excessive heat during low demand and then releasing it during peak demand. However, a phase change material is only one of the components of a latent heat thermal energy storage system. The second part of the latent heat thermal energy storage is a heat exchanger that allows heat transfer between a heat transfer fluid and a phase change material. Thus, the main aim of this review paper is to present and systematize knowledge about the heat exchangers used in the latent heat thermal energy storage systems. Furthermore, the operating parameters influencing the phase change time of phase change materials in the heat exchangers, and the possibilities of accelerating the phase change are discussed. Based on the literature reviewed, it is found that the phase change time of phase change materials in the heat exchangers can be reduced by changing the geometrical parameters of heat exchangers or by using fins, metal foams, heat pipes, and multiple phase change materials. To decrease the phase change material’s phase change time in the tubular heat exchangers it is recommended to increase the number of tubes keeping the phase change material’s mass constant. In the case of tanks filled with spherical phase change material’s capsules, the capsules’ diameter should be reduced to shorten the phase change time. However, it is found that some changes in the constructions of heat exchangers reduce the melting time of the phase change materials, but they increase the solidification time.

Thermal and hydraulic optimization of plate heat exchanger using multi objective genetic algorithm

In this paper thermal and hydraulic optimization of water to water chevron type plate heat exchanger is presented. The optimization is performed using the multi objective genetic algorithm in MATLAB optimization environment. Constrain matrix is a set of different geometrical parameters of plate heat exchanger within the logical bounds. The two objective functions are pressure drop of hot side and heat transfer. Due to conflicting nature of these objective functions, no single solution can satisfy both of the objective function simultaneously. The increase in heat transfer will results in increase in pressure drop, therefore, optimization results are presented as Pareto Front. Multi objective genetic algorithm tool was employed to find a set of optimum solution which was trade-off between pressure drop and heat transfer. At the end, sensitivity analysis was performed to analyse the effect of geometrical parameters of heat exchanger on thermal and hydraulic performance. The sensitivity results show that the heat transfer and pressure drop are greatly affected by the vertical port centre distance, plate spacing and number of thermal plates.

Key parameters effects and design on performances of hydrogen/helium heat exchanger for SABRE

Hydrogen/helium heat exchanger is a kind of heat exchanger dedicated to SABRE (Synergetic Air-breathing and Rocket Engine). Its special working environment and operating condition have brought a great challenge to its design. Hydrogen/helium heat exchanger with micro-channel/plate heat exchanger as its configuration is taken as the research object in this paper. Mathematical model of the heat exchanger is set up based on logarithmic mean temperature difference method, and the parameters that affect the heat transfer performance of heat exchanger is analyzed. The results showed that, reducing the thickness of fin or plate can help reduce the pressure loss of working fluids, the length and weight of hydrogen/helium heat exchanger. Reducing the width of micro-channel can reduce the length of heat exchanger and increase the height of heat exchanger. Reducing the height of micro-channel can reduce the length and height of heat exchanger. As a whole, the pressure loss of working fluids shows a trend of decreasing at first and then rising with the height or width of micro-channel rising. The pressure loss of helium is much greater than that of hydrogen, which means the pressure loss of helium is more sensitive to geometric parameters of heat exchanger and should be well controlled. In order to gain the best performance of the heat exchanger, the geometric parameters of heat exchanger is designed by Artificial Fish Swarm Algorithm.

Thermoeconomic analysis and off-design performance of an organic Rankine cycle powered by medium-temperature heat sources

This paper presents the performance of an organic Rankine cycle (ORC) powered by medium-temperature heat sources. A simulation model, developed by the authors, has been improved to this scope. The model is based on zero-dimensional energy and mass balances for all the components of the system. It is also strictly related to the geometrical and design parameters of its components, especially in case of heat exchangers. The model evaluates the energetic and economic performance of the system, for different operating conditions and design criteria. In particular, the model allows one to set the geometrical parameters of heat exchanger and evaluate the off-design performance of the system. Hence, it could be an useful tool in the preliminary design of the plant. The n-butane has been used as working fluid according to results of the previous authors’ work.Two types of simulations have been performed. The first simulation aims at selecting a design optimization criterion of some geometrical parameters of the shell and tube heat exchangers. The total cost of ORC plant has been selected as objective function. The parametrical analysis has been performed in steady-state regime.The second simulation evaluates the off-design performance of the ORC power plant. The thermal input of the cycle, i.e. diathermic oil coming from the heat source, has been varied in terms of mass flow rate and temperature to analyze the plant response to variations of boundary conditions starting from the design point.With respect to the total cost minimization, as objective function, the simulation results show that for all heat exchangers the higher the heat transfer area, the higher the net power generated and income. Instead, the evaporator shows different trends, hence it represents a key element in ORC design. The geometric optimization of heat exchangers allows the ORC to increase the economic benefit, the net power generated and the global efficiency of about 21.06%, 20.01% and 33.60% respectively.The results of the off-design analysis show that the heat source mass flow rate is a key parameter in net power generation. Fixed the heat source temperature on the upper bound of its variation range (185°C), the net power generation shows both the maximum and minimum value, 335.4kW and 269.3kW, in correspondence of the lowest and the highest value of heat source mass flow rate respectively. Moreover, the results show that the plant efficiency decreases as both heat source mass flow rate and temperature increase. Its maximum value, 14.7%, is achieved for heat source temperature and mass flow rate equal to 155°C and 18kg/s, while its minimum value, 9.54%, is reached for heat source temperature and mass flow rate equal to 185°C and 24kg/s.

Numerical and experimental studies on a two-dimensional model of an offset-strip-fin type compact heat exchanger used at low Reynolds number

Numerical and experimental studies have been made on the flow and heat transfer characteristics of a two-dimensional system with a staggered array of vertical flat plates used in the free-forced mixed convection regime at low Reynolds number. The numerical schemes presently used are validated through the comparisons between their numerical results and the corresponding experimental data which were also obtained in the present study. Through these comparisons, the effects of fin thickness and free-stream turbulence are discussed. Comparisons are also made between the present two-dimensional computation and the experimental data for a practical offset-strip-fin type compact heat exchanger and comments on the effects of three-dimensionality are added. Discussions on the effects of some geometrical parameters of heat exchanger on its performance are finally presented based on the present numerical works.