Enhancement of shell side forced convective heat transfer in the shell tube‐type heat exchanger using thin plate‐type supports

The shell side heat transfer and pressure drop in counterflowing water were experimentally investigated on the basis of the overall heat transfer coefficient. The investigation was intended to identify ways to get higher performance for the cooler in a BWR nuclear power plant. The following three conclusions were reached in the study. (1) Predicted performance of the heat exchanger, using the overall heat transfer coefficient based on the outside area of the tube K_o, indicated an enhancement by 92% compared with the measured performance of the conventional segmental baffle‐type heat exchanger. (2) The tube side pressure drop ΔP_t=20 kPa and the shell side pressure drop ΔP_s=70 kPa were obtained, and were within the allowable value ΔP_a=80 kPa. The shell side pressure drop of the low‐pressure drop spacer could be decreased by 20% as compared with that of the standard spacer. (3) The enhancement constant of the shell side heat transfer using the low‐pressure drop spacer was about 1.2 times as large as that of the standard spacer, regardless of the pumping power. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(5): 455–471, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10097     

Experimental Study on Heat Transfer and Pressure Drop Characteristics of Four Types of Plate Fin－and－TUbe Heat Exchanger Surfaces

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低Re下板式换热器性能的实验研究及热力学分析

实验测定了两种不同板式换热器在低Re条件下(200相似文献   

Numerical estimation of pressure drop and heat transfer characteristics in annular‐finned channel heat exchangers with different channel configurations

In this numerical investigation, three‐dimensional analysis has been used to study the effect of finned channels configuration of (circular, square, and triangular shape) and fin spacing with four rows in staggered arrangements. The finite volume method with k‐ ω turbulent model is applied to estimate the heat transfer and flow characteristics. The results illustrate that the development of the boundary layer between the fins surfaces is credited to the finned channels configuration, fin spacing, and Reynolds number. Moreover, the results of pressure drop and heat transfer with various channel configuration and different fin spacings (1.6, 2, and 4 mm) are presented and validated with the available correlations. The triangular‐finned channel with 1.6 mm fin spacing offered higher heat transfer enhancement followed by square‐ and circular‐finned channels. A considerable agreement was observed when the current findings and the existing correlations were compared, with a maximum deviation of 15% for all the cases.     

Influence of fan setting height on the cooling performance of a plate‐fin‐type heat sink with microprocessor

The cooling performance of a plate‐fin‐type heat sink equipped with a cooling fan was investigated experimentally. The heat sink was 80 mm long, 43 mm wide, and 24 mm in height (including the 4‐mm‐thick base). The cooling fan was 40 × 40 × 15 mm and was set to direct the air flow vertically in the downstream half of the heat sink. We focused on the influence of the height (which varied from 5 to 20 mm) that the fan was set at, on the heat transfer coefficient of the heat sink. The maximum value of the heat transfer coefficient was achieved at a setting height of 5 mm. At this height, the volumetric heat transfer coefficient was 1.8 times as high as that in a parallel flow under the same fan power. This result indicates that the cooling performance of heat sinks with a cooling fan can be improved by using this kind of compact structure. © 2001 Scripta Technica, Heat Trans Asian Res, 30(6): 512–520, 2001     

Effect of the plate thermal resistance on the heat transfer performance of a corrugated thin plate heat exchanger

Two‐dimensional conjugate conduction/convection numerical simulations were carried out for flow and thermal fields in a unit model of a counter‐flow‐type corrugated thin plate heat exchanger core. The effects of the thermal resistance of the solid plate, namely the variation of the plate thickness and the difference of the plate material, on the heat exchanger performance were examined in the Reynolds number range of 100<Re<400. Higher temperature effectiveness was obtained for a thicker plate at any Reynolds number, which was a unique feature of corrugated thin plate geometry. Detailed discussions on the thermal fields revealed that restricting the heat conduction along the plate by making the plate thinner or choosing a low thermal conductivity material causes a larger plate temperature variation along the plate, and, consequently, a smaller amount of thermal energy exchanged between two fluids. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(3): 209–223, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20110     

Thermal design of a closed cabinet with a heat exchanger for inner air cooling

This paper describes a thermal design and simulation method of a closed cabinet with a heat exchanger for inner air cooling. In the controller system that we used for this research, the cabinet is equipped to be outdoors, and the cabinet is sealed to prevent the introduction of dust. Because this system dissipated 630 W in total, it suffered from a problem that the inner air temperature of the cabinet was raised over 30 K. Thus, we installed a heat pipe and heat exchanger in the cabinet, and we also changed the air flow path to realize the best performance of heat exchange according to the results from thermal and fluid simulations using a macroscopic model of heat exchanger to reduce the computational load. We found that the inner air temperature rise was reduced below 15 K, and the measured results were in good agreement with the simulation. © 2001 Scripta Technica, Heat Trans Asian Res, 30(4): 267–279, 2001     

Heat transfer enhancement by using a rectangular wing vortex generator on the triangular shaped fins of a plate‐fin heat exchanger

The present numerical analysis pertains to the heat transfer enhancement in a plate‐fin heat exchanger employing triangular shaped fins with a rectangular wing vortex generator on its slant surfaces. The study has been carried out for three different angles of attack of the wing, i.e., 15°, 20° and 26°. The aspect ratio of the wing is not varied with its angle of attack. The flow considered herein is laminar, incompressible, and viscous with the Reynolds number not exceeding 200. The pressure and the velocity components are obtained by solving the continuity and the Navier– Stokes equations by the Marker and Cell method. The present analysis reveals that the use of a rectangular wing vortex generator at an attack angle of 26° results in about a 35% increase in the combined spanwise average Nusselt number as compared to the plate‐triangular fin heat exchanger without any vortex generator. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20285     

Comparative study of mechanical and chemical methods for surface cleaning of a marine shell‐and‐tube heat exchanger

In this article, experimental analysis is done on shell‐and‐tube heat exchanger of a marine vessel for removal of fouling using optimum surface‐cleaning techniques. The main objective is to compare the performance of the heat exchanger before and after maintenance. Two identical deteriorated systems of heat exchangers are taken and real‐time analysis is conducted. The log data are taken before and after undergoing maintenance for the two systems. Two different cleaning techniques are used, namely, chemical cleaning and mechanical cleaning. Detailed calculations are made for the shell‐and‐tube heat exchanger. From the obtained data, comparisons are made for different parameters on the tube side such as friction factor, heat transfer coefficient and pressure drop, as well as total heat transfer rate on the shell side. From the analysis and comparison, it was found that greater heat transfer takes place for the tubes cleaned using the chemical cleaning method than for tubes cleaned by the mechanical cleaning method. Pressure drop is found to be less for chemical cleaning method than mechanical cleaning method. This indicates that the fouling effect is reduced for tubes cleaned by the chemical cleaning method, and furthermore these tubes remain corrosion‐resistant for longer periods of time.     

Use of high performance plate heat exchangers in chemical and process industries

At present, plate heat exchangers constantly open up new application fields in the chemical, process, and allied industries due to their numerous advantages. The channel flow between individual plates is characterized by high turbulence induced at low flow velocities. Heat transfer coefficients are generally higher in plate heat exchangers than in conventional shell-and-tube heat exchangers. According to the nature of the process, physical properties of the media, and allowable pressure drops, plates with a variety of patterns are available to adapt the equipment optimally to the specific process conditions. For handling aggressive media the module welded plate heat exchanger was developed. The laser welded modular design keeps the inherent advantages of plate type heat exchanger. It can be disassembled and mechanically cleaned outside the modules. The capacity can also be subsequently modified by changing the number of plates, or the plate patterns can be altered as it can be with the gasketed units. Typical applications of module welded plate heat exchangers in the chemical industry are acid coolers, thermal oil coolers, or condensers for hydrocarbon mixtures.     

Experimental study on the effect of porous medium on performance of a single tube heat exchanger: A CO2 case study

An experimental study on single‐phase laminar forced convection in a single porous tube heat exchanger is presented. Parametric studies are conducted for different inlet pressures, different mass flow rates, and different porosities to evaluate the effects of particle diameter and Reynolds number on the heat transfer and friction factor. The Nusselt number and friction factor are developed for efficient design of a porous heat exchanger based on the present configuration. Heat is transferred to the walls of the heat exchanger by natural convection mode. Gravel sand with different porosities is used as a porous medium during the tests. The flow of carbon dioxide as a working fluid in the porous medium is modeled using the Brinkman–Forchheimer‐extended Darcy model. A dimensionless performance parameter is developed in order to be used in evaluating the porous tube heat exchanger based on both the heat transfer enhancement and the associated pressure drop. The study covers a wide range of inlet pressures (P_i), mass flow rates ( ), porosity of gravel sand (ε), and particle diameters (d_m) which ranged 34.5 ≤ P_i ≤ 43 bars, 8 ?? 10^?5 ≤ ≤ 16 ?? 10^?5 kg/s, 34.9% ≤ ε ≤ 44.5%, 1.25 ≤ d_m ≤ 5.15 mm, respectively. This study revealed that a smaller particle diameter can be used to achieve higher heat transfer enhancement, but a larger particle diameter leads to a more efficient performance based on heat transfer enhancement. The average heat transfer coefficient of carbon dioxide decreases when the porosity increases. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21059     

The heat transfer and pressure loss characteristics of a heat exchanger for recovering latent heat (the heat transfer and pressure loss characteristics of the heat exchanger with wing fin)

In recent years the requirement for reduction of energy consumption has been increasing to solve the problems of global warming and the shortage of petroleum resources. A latent heat recovery type heat exchanger is one of the effective methods of improving thermal efficiency by recovering latent heat. This paper described the heat transfer and pressure loss characteristics of a latent heat recovery type heat exchanger having a wing fin (fin pitch: 4 mm, fin length: 65 mm). These were clarified by measuring the exchange heat quantity, the pressure loss of heat exchanger, and the heat transfer coefficient between outer fin surface and gas. The effects of condensate behavior in the fins on heat transfer and pressure loss characteristics were clarified. Furthermore, the equations for predicting the heat transfer coefficient and pressure loss which are necessary in the design of the heat exchanger were proposed. ©2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(4): 215–229, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20154     

Experimental research on the effects of distributor configuration on flow distribution in plate‐fin heat exchangers

The effects of different distributor configurations on the flow distribution in plate‐fin heat exchangers were studied. It was found that an irrational distributor configuration would lead to the flow maldistribution and a different degree of non‐uniformity of the flow distribution in the transverse and longitudinal directions. The distributor configuration and Reynolds number are the main factors affecting the flow distribution. An improved distributor configuration with a fluid complementary cavity has been brought forward. The experimental results showed that the improved distributor configuration can effectively improve the performance of flow distribution in heat exchangers. The best performance of flow distribution was obtained at h/H = 0.2. The correlations between the flow maldistribution characteristic and the flow Reynolds number for different distributor configurations were deduced according to the experimental data. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(6): 402–410, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20023     

Multiobjective thermo‐economic and thermodynamics optimization of a plate–fin heat exchanger

In the present work, a multiobjective heat transfer search (MOHTS) algorithm is proposed and investigated for thermo‐economic and thermodynamic optimization of a plate–fin heat exchanger (PFHX). Heat exchanger effectiveness and total annual cost (TAC) are considered as thermo‐economic objective functions. Similarly, entropy generation rate and heat exchanger effectiveness are considered as thermodynamic objective functions. Six design variables including flow length of cold and hot streams, no flow length, fin height, fin pitch, and fin offset length are considered as decision variables. Effectiveness and accuracy of the proposed algorithm are evaluated by analyzing application examples of a PFHX. The results obtained using the proposed algorithm for thermo‐economic considerations are compared with the available results of NSGA‐II and TLBO in the literature. Results show that 3.56% to 10.29% reductions in TAC with 0.48% to 0.81% higher effectiveness are observed using the proposed approach compared to TLBO and NSGA‐II approaches. Additionally, the distribution of each design variable in its allowable range is also shown for thermo‐economic consideration to identify the level of conflict on objective functions. The sensitivity analyses of design variables on the objective functions value are also performed in detail.     

低气压环境下开缝翅片管换热器换热性能研究

利用低气压环境模拟装置对开缝翅片管换热器在不同气压下的换热性能进行实验研究.研究结果表明:随着气压不断降低,换热器周围空气密度逐渐降低,换热器空气侧换热系数以及显热换热量逐渐降低,而空气含湿量随着气压降低逐渐升高,导致潜热换热量逐渐增加;当气压降至0.058 MPa以下时,换热器空气侧潜热换热量占主要部分,当气压为0.04 MPa时,换热器换热能力与常压下相比下降了36.63%.     

Effect of fins on forced convection heat transfer around a tube in an aligned‐arranged tube bundle

The effect of fins on heat transfer around a tube in an aligned‐arranged tube bundle was investigated experimentally, and the obtained results were compared for three arrangements, i.e., single tube, single tube row, and staggered‐arrangement. It was found from the experiment that the effect of fins begins to appear in an aligned‐arrangement with larger fin spacing than in a staggered‐arrangement. The degradation in the local heat transfer coefficient due to fins can be recognized not only on the rear region of the tube, as observed in other arrangements, but also on the frontal region. As a result of this phenomenon, the degradation in the average heat transfer coefficient in an aligned‐arrangement becomes larger than in other arrangements with the same fin spacing. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(8): 555–563, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20091     

A simple method for predicting the performance of a heat exchanger mounted in an air conditioner (1st report,proposed reduced‐mesh analysis modeling method)

To analyze the performance of a heat exchanger (HEX) used in air conditioners within a realistic time frame, a simple method—based on a reduced‐mesh calculation model—was developed. The pressure loss caused by the HEX is given by a momentum source term, and the heat‐transfer performance of the HEX is approximated by using a wall function as the boundary condition. The analytical results from this simple analysis model (under a fin‐pitch range of 1.0 to 1.6 mm) were compared with experimental measurements of pressure loss and heat‐transfer performance. This comparison showed that the pressure loss from the simple analysis model agrees with the experimentally measured loss (within 3% error) and that the heating capacity determined by the simple model agrees with the experimentally measured one (within a 1% error). © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(1): 12–23, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10130     

Thermal performance analysis of plate heat exchanger with different configurations for the heat recovery system in buildings

Due to the scarcity of conventional energy sources, a lot of efforts need to be taken regarding energy conservation in the buildings, including heat recovery of air ventilation systems. The present paper focuses on new methods to improve the thermal performance of the heat recovery system by investigating the heat transfer characteristics and the flow development in a flat-plate heat exchanger (FPHE) using three different rib-grooved surfaces (trapezoidal, triangle and semi-circular), the numerical simulations were carried out for uniform wall heat flux equal to 290 W/m² for air as the working fluid, the Reynolds number varies from 500 to 2000 for three different channel heights. The numerical results indicated that, rib-grooved surfaces have a significant impact on heat transfer enhancement with an increase in the pressure drop through the channel. The effect of rib-grooved patterns on the heat transfer and the fluid flow is more significant in a narrow channel especially for trapezoidal and triangle corrugated surfaces, because they have sharp edges. Based on the present research, the FPHEs with the added rib-grooved surfaces are recommended to provide an efficient and compact heat recovery system. Moreover, it was found that by applying the new design, a considerable amount of energy and power could be saved.     

Thermal performance investigation of SWCNT and graphene quantum dots nanofluids in a shell and tube heat exchanger by using fin blade tubes

The experimental study, thermal performance, and pressure drop of single-walled carbon nanotube (SWCNT) and graphene quantum dot (GQD) nanofluids in shell and tube heat exchanger with fin blade tubes are evaluated. The effects of the working fluid (water) volume flow rates ($\dot{V}=$ 2.5–10 L/min), volume concentration of nanoparticles ($\omega =$ 0.0%, 1%, 3%, and 5%), Reynolds number of working fluid (Re = 850–3300), and tube building (heat exchanger with fin blade tubes and without fin blade tube) have been analyzed. Results represent that with augmentation of volume concentration of SWCNT nanoparticle up to 1%, heat transfer rate increases by ∼5% and then up to 5% volume concentration of SWCNT nanoparticle decreased about 17%, also this calculation for GQD nanoparticle conducted and results represented decreasing 6% and approximately unchanged heat transfer rate, respectively. With regard to obtained results, heat transfer rate of heat exchanger can be improved by using the fin blades by 188%, compered without fin blade heat exchanger also most related increase for pressure drop of heat exchanger was recorded about 80% for 5% SWCNT of nanofluid. At the end, the mean enhancement in effectiveness of heat exchanger with various concentrations of SWCNT and GQD nanofluids and using the fin blades is about over 100% and 85%, respectively. In fact, the present study shows that applying the new finned tubes in the heat exchanger has more impact, related to the mentioned nanoparticles on the thermal properties of heat exchanger.     

Prediction of heat exchanger performance by the thermal network method (Improvement of an evaporator's performance and restraining air flow bypass by adjusting the refrigerant‐flow path pattern)

This paper presents the influence of latent heat load by changing the relative humidity of air flow distribution in the super‐heated gas region in an evaporator and the effect of the refrigerant flow path pattern. To estimate the influence, we applied the thermal network method that can consider refrigerant quality distribution in the heat exchanger. If the super‐heated gas region spreads to the upper wind row, humid air goes through the heat exchanger without drying, called “air flow bypass.” To suppress this phenomenon and simultaneously obtain the best performance, we chose an optimum path pattern on the basis of this method. As a result, the prediction shows that performance of the evaporator is recovered 5% for a simple 2‐row 2‐path heat exchanger when 40% of the unbalance of air flow rate occurs. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20302