Cross-flow Plate Research Articles

Study on the thermal performance of the cross-flow plate heat exchangers

The exhaust gas emitted by a stenter machine will lead to energy waste and environmental heat pollution. Therefore, designing an efficient waste heat recovery apparatus for exhaust gas not only protects the environment but also saves production costs. In the article, the heat transfer performance and pressure drop of three types of heat exchangers: flat-plate heat exchanger (PHE), wavy-PHE, and zigzag-PHE were numerically studied in the context of waste heat recovery from the exhaust gas of stenter machines. The heat transfer rate (Q), Nusselt number (Nu), Colburn factor (j), pressure drop, Fanning friction factor (f), and comprehensive performance factor (JF) were investigated while Reynolds numbers ranged from 1000 to 9000. An experimental measurement was devised to validate the accuracy of the numerical simulation. The results of the research indicate that the wavy-PHE exhibits improved heat transfer efficiency and reduced pressure drop, primarily attributed to the substantial generation of secondary flow. Three new correlations for Nusselt number in different PHEs were developed based on commonly existing empirical formulas. The prediction accuracy for the Nusselt number based on the new correlations has been significantly improved in the present study.

Peculiarities of thermal calculation of cross-flow plate air recuperators

Application of modern energy-saving technologies is the most important task in development of construction industry. In the conditions of exhausting decrease of energy consumption of public, administrative buildings due to reduction of transmission heat losses the implementation of mechanical ventilation with recuperation of exhaust air heat becomes a rational way to increase energy efficiency. One of the key problems in the study of plate-type air recuperators is to find the temperature efficiency of the device. The value of this characteristic is influenced by such parameters as the area of the branched heat exchange surface, initial temperatures of heat carriers, volume flow rates, flow rate ratio, type of fins, etc. The purpose of the study is to compare coefficients of thermal efficiency of outside air as a function of Reynolds number obtained by engineering calculation, mathematical modelling and manufacturer’s data for the recuperator ISIS Recover HR-A-05-V-G4-E-1-60. The article substantiates the calculation method using the existing algebraic dependence describing heat transfer in the cross-flow scheme of coolant motion on the basis of new results. An empirical dependence is obtained, which adequately describes the results of numerical simulation using the ANSYS Fluent solver and engineering calculation.

Modelling an air handling unit, building and occupant variation regarding energy, moisture and frost protection based on measurements of an air handling unit and occupants’ moisture supply

Objectives of this paper are to propose a reasonable simulation model that can handle condensation and frost formation in heat exchangers dependent on moisture concentration and outdoor climate conditions, and to analyze risk of frost formation and discuss different frost protection strategies. Using psychometrics, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) heat exchanger calculation, condensation and frost calculation methods, simulations models for heat recovery ventilation and energy recovery ventilation are developed. It is concluded that the risk of frost in heat exchangers is higher in northern Sweden than in southern Sweden and Denmark due to low outdoor air temperatures during the winter, however heat recovery systems in Copenhagen and Gothenburg still has a risk of frost formation even though these cities has relatively warm weather conditions. Out of several simulation models that are created during the study, the detailed model that takes condensation effect into consideration, is proven to be worthy to be used in further investigations, due to results that more accurately represent real word conditions. Risk of frost formation becomes significantly lower in every city when heat recovery ventilation is changed into energy recovery ventilation. Even though heat recovery ventilation is simulated only with the simplified model, it is safe to assume that it will still be effective in reality. Although bypass strategies were effective at eliminating the risk of frost in heat recovery units, they are not as efficient from an energy perspective. The more air is by-passed through the cross-flow plate heat exchanger, the fewer opportunities there are to recover energy from exhaust air, which leads to lower supply air temperatures and higher energy need for heating a living space.

Comparison of the Efficiency of Cross-Flow Plate Heat Exchangers Made of Varied Materials

This paper discusses a mathematical model for airflow through a cross-flow plate heat exchanger. The exhaust air is used to heat the supply air. Three kinds of plates are considered: made of aluminium, copper, and steel. The purpose of this research was to verify which material used to build the plate heat exchangers uses the exhaust air heat more efficiently. The method of the Trefftz function was used to determine approximate solutions to the analysed problem. The results obtained for 1.2 mm-thick plates and for external winter, summer, and spring–autumn temperatures are discussed. The results indicate that if the efficiency and price of the metals are considered, then steel is the best material for the plate heat exchanger. Thanks to the use of thin steel plates and the reduction in air exchange time to a few minutes, a cheap and efficient cross-flow heat exchanger can be obtained.

Thermodynamic characteristics of counter flow and cross flow plate fin heat exchanger based on distributed parameter model

The distributed parameter models of counter flow and cross flow plate fin heat exchanger (PFHE) are constructed to investigate their thermodynamic characteristics. In practical application, the cold end of PFHE may be directly connected to the cold equipment. Therefore, the effect of longitudinal heat conduction (LHC) under different thermal boundary conditions set on two ends of the separating plates (SPs) is investigated based on the model of counter flow PFHE. It is found that LHC effect transmits the effect of boundary condition on two ends of the SPs into the inner domain of PFHE. The LHC effect on the heat transfer performance of PFHE is positive when setting appropriate boundary condition on two ends of the SPs. When considering LHC, compared with the adiabatic boundary conditions on two ends of the SPs, the effectiveness of constant wall temperature boundary conditions increases by 31.7 ∼ 35.8 %, and the effectiveness of constant heat flux boundary conditions increases by 22.8 %. The model of cross flow PFHE is used to investigate the effect of configuration and operation parameters on the heat transfer amount and the pump power. The cross flow PFHE is optimized to arrive at the maximization of heat transfer amount per unit pump power (HTPUP). In the three-stream cross flow PFHE studied, the heat transfer amount almost doesn’t change when the xz projected area is maintained and one projected length (z side length) is changing. The pump power is the lowest and the HTPUP is the largest when z side length of PFHE (z side is the flow direction of the fluid with large mass flowrate) is 0.15 ∼ 0.2 m.

Thermal-Economic Optimization of Plate–Fin Heat Exchanger Using Improved Gaussian Quantum-Behaved Particle Swarm Algorithm

Heat exchangers are usually designed using a sophisticated process of trial-and-error to find proper values of unknown parameters which satisfy given requirements. Recently, the design of heat exchangers using evolutionary optimization algorithms has received attention. The major aim of the present study is to propose an improved Gaussian quantum-behaved particle swarm optimization (GQPSO) algorithm for enhanced optimization performance and its verification through application to a multivariable thermal-economic optimization problem of a crossflow plate–fin heat exchanger (PFHE). Three single objective functions: the number of entropy generation units (NEGUs), total annual cost (TAC), and heat exchanger surface area (A), were minimized separately by evaluating optimal values of seven unknown variables using four different PSO-based methods. By comparing the obtained best fitness values, the improved GQPSO approach could search quickly for better global optimal solutions by preventing particles from falling to the local minimum due to its modified local attractor scheme based on the Gaussian distributed random numbers. For example, the proposed GQPSO could predict further improved best fitness values of 40% for NEGUs, 17% for TAC, and 4.5% for A, respectively. Consequently, the present study suggests that the improved GQPSO approach with the modified local attractor scheme can be efficient in rapidly finding more suitable solutions for optimizing the thermal-economic problem of the crossflow PFHE.

Optimization of Parameters to Improve Effectiveness of Plate and Fin Heat Exchangers using Taguchi Method and CFD Analysis

Radiators are a type of cross-flow plate and fin heat exchangers used for cooling purposes. This paper describes the investigation of the cooling science behind it as an integration of forced convection and heat transfer. Radiators are used for the cooling various machinery from automotive engines to heavy-duty industrial applications like excavators and so on. There haven’t been major developments in the radiator design in recent times on a commercial basis concerning an increment in efficiency. Thus, the following research study aimed to explore the feasibility of enhancing radiators’ effectiveness by integrating a variety of theoretical and simulation models, namely Taguchi Design, Ԑ-NTU method for numerical analysis and validation by CFD analysis.

Cross-flow plate reactor for ethanol steam reforming: A theoretical study

In this contribution, a theoretical study of ethanol steam reforming (ESR) over a Pd-based catalyst in a plate microreactor is carried out. ESR is convectively heated by means of a flue gas stream flowing through contiguous plates in a cross-flow configuration.To describe the performance of the reactor under steady-state adiabatic operation a pseudo homogeneous 2D model is considered. The influence of the main operating variables and the different flue gas feed arrangements on the performance of the reformer has been analysed with the aim of accomplishing a total hydrogen production of 1 kWth.The results show that the cross-flow plate reactor is a promising design to carry out the ESR under operating and design conditions that favour thermal homogeneity (high heat transfer) and a high enough residence time of the reactants in the reforming side.

Numerical analysis of cross-flow plate type indirect evaporative cooler: Modeling and parametric analysis

This paper focuses on numerical modeling of heat and mass transfer characteristics within a plate type cross-flow indirect cooling system considering the impact of the surface wettability factor. For this objective, a numerical model is developed to implement the heat and mass transfer process calculations inside the indirect cooling system. The mathematical model validated by published data from literature with a perfect convention. To specify the parameters that significantly affect the indirect evaporative cooling system’s performance, precise analysis is executed by employing three evaluation indexes, including the average outlet temperature of the product air stream, cooling capacity rate, and wet-bulb efficiency. The simulation results showed that the surface wettability factor greatly influences the performance of IECs. Moreover, improving the wettability factor has a positive influence on enhancing the cooling capacity and wet-bulb efficiency. When the wetting factor is increased from (0.5–1.0) the wet-bulb efficiency increased from 69% to 92%, respectively, and the average outlet temperature decreased from 27 °C to 24 °C. Furthermore, the heat and mass transfer performance strongly relies on the air inlet temperature, the intake velocity, mass flow rate, and working air humidity ratio.

Analytical solution for heat transfer problem in a cross-flow plate heat exchanger

Cross-flow plate heat exchangers are used for plenty of applications in industrial and domestic sectors, and the analysis of heat transfer is a key for the evaluation of their performance. There are challenges for an analytical study because heat transfer in each channel is governed by a partial differential equation coupled with temperature fields in the adjacent channels representing a three-dimensional problem. The problem is even more complicated in the turbulent regime as the effective thermal diffusivity varies within the channel cross-section. In the present study, a separate set of governing equations and boundary conditions are considered for each part of the heat exchanger. Appropriate profiles for the flow velocity and thermal diffusivity are substituted into the governing equations of the channels. The resulting partial differential equations in the channels are solved using the separation of variables method. There remains an unknown boundary condition linked to the temperature field on the plate surface which is considered to be in the form of a two-variable series function whose coefficients are calculated by applying energy balance between the two sides of the plate. The obtained solution provides explicit expressions for the temperature fields in the plate and channels. A scaling analysis is conducted showing that the model is valid when Peclet numbers in both hot and cold channels are not small. The results are compared with empirical data and a numerical model, and the accuracy of the derived heat transfer coefficients is investigated. In harmony with the scaling analysis, a close agreement is observed in both laminar and turbulent flows for moderate and high Prandtl numbers and when Peclet number is greater than 1000 in the case of turbulent flow.

다중이용업소의 환기방법에 따른 냉·난방에너지 소비량

Recently, the pandemic virus COVID-19 causing many infections and cases of infection by from being in the same space with an individual or individuals without direct contact has been alarmingly increasing. Referring to COVID-19’s virulent propagation mechanism, it may be inadequately safe to maintain a distance of 1 to 2 m from an infected person to prevent infection, and frequent, effective ventilation is necessary to remove more virus particles. In this paper, a cafe was selected as a typical multi-use store. TRNSYS18 was used to compare and analyze the heating and cooling load values with the different types of ventilation methods. The analyses were: ventilation not performed, forced ventilation performed at 1500 CMH continuously for 24 hours (simple forced ventilation), forced ventilation according to the concentration of CO₂ (reasonable forced ventilation), ventilation using a crossflow plate, and rotary energy recovery ventilation. Compared to the reasonable forced ventilation, the plate and the rotary energy recovery ventilation showed reduction ratios of 6.3% and 20.9% respectively. The heating loads increased by 16.1 times for simple forced ventilation and 6.2 times for reasonable forced ventilation compared to when ventilation was not performed. Conversely, the plate and the rotary energy recovery ventilation showed an increase of approximately two times only.

Study on mass transfer time relaxation parameter of indirect evaporative cooler considering primary air condensation

Air condensation phenomenon occurs when the indirect evaporative cooler (IEC) is applied in high temperature and humidity regions, where indoor exhaust air is used as secondary air to pre-cool the fresh air (primary air) in an air conditioning system. The mass transfer time relaxation parameter (β) in the phase change coefficient model (Lee model) is a key parameter in the coupled heat and mass transfer mechanism of IEC. As β is difficult to be obtained by theoretical calculation, the influence of β on the temperature and humidity parameters at the primary outlet of IEC heat exchanger is determined by experiments, and the piecewise fitting function of β on the inlet temperature of primary air is given. In view of the unsteady temperature evaporation condensation process of water in the primary channel and the heat and mass transfer process of the spraying liquid film in the secondary channel, β is applied to a computational fluid dynamics (CFD) model of a three-dimensional cross-flow plate IEC heat exchanger. The physical model of the improved three-dimensional cross-flow plate heat exchanger is verified and the error analysis is carried out. The results show that the accuracy of the model is greatly improved with a discrepancy of less than ±10% under different working conditions.

Performance enhancement of cabinet cooling system by utilizing cross-flow plate heat exchanger

Gas-gas plate heat exchanger is an important component to remove heat generated from electronic devices in the cabinet cooling system. The counter-flow plate heat exchanger is usually used due to its higher heat transfer performance than the cross-flow plate heat exchanger. However, in the cabinet cooling system, the overall dimensions for the heat exchanger is limited. Therefore, it is necessary to consider the overall dimensions of the system during heat exchanger design, but the traditional thermal design method of heat exchanger doesn’t consider the effect of system parameters. In this paper, a cross-flow plate heat exchanger is proposed to improve the cooling performance of cabinet cooling system, and is compared with the counter-flow plate heat exchanger. The ε-NTU method and effectiveness-thermal resistance method are applied to evaluate the performance. It is found that for large width of cabinet cooling system, the system with cross-flow plate heat exchanger has higher cooling performance and lower thermal resistance than the system with counter-flow plate heat exchanger. When the width is 700 mm, the cooling capacity of the two systems are 176.13 W/K and 138.95 W/K, respectively. The dimensionless thermal resistance can characterize the irreversibility of the heat transfer at constant mass flow rate.

A Three-Dimensional Thermo-hydrodynamic Simulation of Compact Cross-Flow Plate Heat Exchanger

This study is dedicated to the thermal analysis and thermo-hydrodynamic simulation of an air-to-air plate heat exchanger in order to solve its routine problem in industry. The compact type of cross-flow plate heat exchanger, in which corrugated plates pile up tightly and delicately brazed to each other, has been used in many situations and has many applications from food industries to petroleum and military. Routinely, after a certain lifespan, the brazed joints are detached and cause a mixture of hot and cold fluids as well as highly reduction of heat exchanger performance. This problem leads to increase the system maintenance significantly. Apart from the imposed cost and time for its maintenance, which is indeed a crucial problem? Finally, to have a better understanding, a threedimensional numerical investigation on thermo-hydrodynamic analysis of conjugate heat transfer was performed using computational fluid dynamics techniques. Forced convection heat transfer for fluid flow and conduction through solid material were considered as well. For simulation of steady state flow of Newtonian fluid, the governing equation was discredited by finite volume method and solved by the semi-implicit method for the pressure-linked equation. It was also found that both temperature and temperature gradient play an important role in this problem.

A novel single and multi-objective optimization approach based on Bees Algorithm Hybrid with Particle Swarm Optimization (BAHPSO): Application to thermal-economic design of plate fin heat exchangers

As a novel hybrid optimization approach, the single and multi-objective BAHPSO are investigated for thermal designing of the cross-flow plate fin heat exchanger (PFHE) under given heat duty and pressure drop constraints. Because both of the Particle Swarm Optimization (PSO) and Bess Algorithm (BA) are operating with a random primary population of solutions, the current study combined their searching abilities for the first time, and presented a novel searching procedure named BAHPSO. In the current investigation, Multi-Objective optimization (MO) of BAHPSO is simultaneously employed to acquire the maximum effectiveness and the minimum total annual cost (TAC) of a heat exchanger as two contradict objectives and then results are compared with MOPSO and MOBA. Hot and cold side length, fin frequency, number of fin layers, fin thickness, fin height, and fin lance length are chosen as seven decision parameters. Also, a sensitivity analysis is performed to study the impact of geometrical parameters on each objective function. Finally, accuracy and efficiency of the presented algorithm is proven via illustrative single-objective optimization case studies which adopted from the references. Results demonstrate that the BAHPSO can detect optimal shape with higher accuracy compared to other algorithms.

Numerical analysis of the heat recovery efficiency for the post-combustion flue gas treatment in a coffee roaster plant

The heat recovery system for the post-combustion flue gas treatment in a coffee roaster plant is investigated using both a lumped and distributed parameter numerical modelling and a transient CFD approach. The combined analysis of the two numerical approaches enables to estimate the thermo-pneumatic behaviour of the entire plant as well as the optimal design of the heat exchanger.The effects of the heat recovery are evaluated in terms of improved energy efficiency and reduction of the fuel consumption. The counter-flow shell and tube and cross-flow plate fin heat exchangers are designed in order to have similar performance in terms of recovered heat and their performance on the real plant is predicted under actual plant operations. The overall volume of the plate fin device results to be approximately one tenth of the shell and tube architecture's volume, while the pressure drop of the two systems is comparable.Finally, the heat recovery from the flue gas enables to save up to 27% of the fuel necessary to power the post-combustor adopted for the exhausts' treatment and up to 13% of the total fuel consumption of the plant.

Analysis of the frost formation and freeze protection with bypass for cross-flow recuperators

A theoretical analysis of coupled heat and mass transfer inside the cross-flow plate heat exchanger used for energy recovery under frosting operating conditions was presented. Three selected frost control techniques were analysed on the base of original ε-NTU model. Frost-free operating conditions were determined for the cross-flow plate heat exchanger under different opening levels of bypass damper and face and bypass dampers. It was found that the implementation of the particular variant of heat exchanger performance and the values of critical outdoor temperatures for different operating conditions in which the onset of frosting occurs in the cross-flow flat plate heat exchanger depend upon the heat and mass transfer conditions realized in two decisive points on the return air channel surface known as the “cold corner” and “hot corner”. It was concluded, that the fully open bypass technique does not provide complete frost protection under sub-zero outdoor air temperature operating conditions.

Experimental Investigation of Thermal Behavior of Cross Flow Plate-fin Heat Exchanger with Offset Strip Fin

The Present work is carried out to investigate the thermal behavior of cross flow plate fin heat exchanger having offset strip fin. An experimental set up has been built in the laboratory to test the Plate fin Heat exchanger. Sets of experiments had conducted to determine the thermal performance of the given heat exchanger. Mass flow rate of cold fluid, mass flow rate of hot fluid, hot fluid inlet temperature, cold fluid inlet temperature, hot fluid and cold fluid inlet pressure are considered as input parameters. The values of the heat transfer co-efficient, effectiveness and pressure drops are obtained for the different value of the input parameters. The experimental results are compared with the correlations developed by Maiti and Sarangi, Manglik and Bergles and Joshi and Webb. Finally, based on the experimental results coluburn factor (j) correlation is developed to predict the value of heat transfer co-efficient.

Improving exergetic performance parameters of a rotating-tray air dryer via a simple heat exchanger

In this study, exergy analysis was applied for a rotating-tray dryer equipped with a cross-flow plate heat exchanger during drying of apple slices. Three drying air temperatures and tray rotation speeds in the range of 50–80 °C and 0–12 rpm, respectively, were employed. Two drying air velocities in the range of 1–2 m/s were adjusted for each drying temperature and rotation speed with and without application of the heat exchanger. The experiments were conducted to assess the effects of the experimental variables on the exergetic performance parameters of the dryer. Also, the effect of drying conditions on the quality of dried apple slices was assessed by determining rehydration ratio, apparent density, shrinkage, and surface color. In general, the exergetic performance parameters of the dryer depended profoundly on the drying air temperature and velocity. Interestingly, the exergetic efficiency of drying process was significantly improved from a minimum value of 23.0% to a maximum value of 96.1% by using the heat exchanger. Furthermore, the incorporation of heat exchanger did not negatively affect the quality of dried product. Therefore, the strategy presented herein could be a promising approach for waste energy recovery in drying without any unfavorable change in the quality of dried product.

Frost formation in the cross-flow plate heat exchanger for energy recovery

The paper is focuses on the numerical simulation and analysis of coupled heat and mass transfer under ice formation conditions in the cross-flow plate heat exchanger. The simulation is performed using the original mathematical model. The presented model was validated against experimental data. The obtained results showed satisfactory agreement with the data obtained from the experimental measurements. Numerical simulation reveals many unique features of considered heat exchanger connected with the heat and mass transfer occurring in the return air channel under ice formation conditions. The results of computer simulation showed that the efficiency gains are sensitive to various inlet conditions, and allow for estimation of the safe operating conditions for different inlet return airflow parameters, based not only on the exhaust air temperature but also on its relative humidity and different thermal efficiency of the exchanger. Several goals were achieved, including: establishing the most unfavorable operating conditions (from the standpoint of ice formation on the plate surface of the return air channels) for cross-flow plate heat exchanger, which correspond to the inlet value of the return airflow dew point temperature equaled to 0°C, impact of the ice formation on temperature effectiveness, impact of inlet relative humidity on temperature effectiveness and safe operating conditions and safe operating conditions for variety of inlet exhaust air parameters.