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This work addresses heat transfer in channels fitted with heat-conducting fins inserted in both walls, transversally to the flow direction, in a staggered arrangement. Turbulent fluid flow and conjugate heat transfer are assumed in the simulations. The hydrodynamic (pressure coefficient) and thermal (Nusselt number) behavior of the heat exchanger is investigated for different values of fin thickness, inclination angle and blockage ratio. The simulations show that the geometrical parameters of the finned channel cause changes in the flow topology, which in turn leads to significant differences in pressure drop and heat transfer rate. It is observed that the fin blockage ratio imposes the greatest effect in the hydrodynamic and thermal problems, followed by the fin inclination angle and thickness.

In this paper, steady state sensible performance analysis on multi pass parallel cross flow exchanger was considered. The inputs to the heat exchanger were described through meaningful physically significant parameters such as number of transfer units, capacity rate ratio and dimensionless input temperature. The inputs to the heat exchager were varied systematically and a parametric study was conducted to determine the thermal performance at each individual pass of the heat exchanger. Heat exchanger’s thermal performance was described through the discharge temperatures that were expressed in a dimensionless form. The results from the study were presented in the form of performance tables. The performance tables employed meaningful and industry recognized dimensionless input parameters and the heat exchanger‘s performance was described through dimensionless discharge temperatures at every pass of the heat exchanger. The developed performance tables shall serve two critical aspects. First, it will help the heat exchanger designers to readily choose an optimum heat exchanger. An undersized heat exchanger shall not deliver the requirements and likewise an oversized heat exchanger shall add unnecessary weight and cost. This aspect was clearly observed in this study as indefinetly increasing the number of transfer units (or surface area) beyond a threshold value didn’t enhance the heat transfer. By employing the performance tables as a guide, the heat exchanger designers can quickly ascertain the performance of the heat exchanger without having to perform simulations and/or lengthy calculations. Second, during operational phase of the heat exchanger, the performance tables can be used to understand the performance variation of the heat exchanger with respect to mass flow rates and/or can help the engineers to choose appropriate mass flow rates for the required heat transfer. The highest heat exchanger performance was observed at the lowest capacity rate ratio and likewise the lowest heat exchanger performance was observed at the highest capacity rate ratio. In-addition, during the operational phase, the performance tables can help to detect an underperforming heat exchanger and can help the engineers to schedule maintenance activity on the heat exchanger equipment.

This study deals the purpose of optimal values of the design constraints in a Plate Heat Exchanger by using Response Surface Method (RSM). The special effects of design constraints such as Reynolds number, flow velocity and pressure drop are examined. In the Reference Surface Method experimental design method, Nusselt number and friction factor are considered as performance parameters. The analysis of Reference Surface Method conducted with an optimization process to reach minimum pressure drop (friction factor) and maximum heat transfer (Nusselt number) for the designed Plate heat exchanger. Experimental results authorized the correctness of the planned method. Design expert 7.0 has been used for optimization process. Optimal values are selected from highest desirability value which is 0.80161 and design constrains has been optimized as 1600(Reynolds number), 0.04 m2 (Core area), 1.24 m (Core length).

As an efficient heat conducting unit, micro heat pipe is widely used in high heat flux microelectronic chips, and thermal resistance is one of the factors that are crucial to its heat transfer capacity. Based on heat transfer theory, this paper established a theoretical model of total thermal resistance through analyzing the structure and heat transfer performance of circular heat pipe with trapezium-grooved wick, simplified the model and tested the micro heat pipe for its total thermal resistance performance by setting up a testing platform. The testing results show that when the micro heat pipe is in the optimal heat transfer state, its total thermal resistance well coincides with that from the established theoretical model. As for a micro heat pipe with trapezium-grooved wick, its total thermal resistance first decreases, then increases with heat transfer capability increment, and reaches the minimum when it is in the optimal state of heat transfer performance. That too much working fluid accumulates in evaporation section and the vapor velocity is rather low is the main cause for the greater thermal resistance when the pipe is in low heat transfer quantity, yet the greater total thermal resistance when the pipe is in high heat transfer quantity is mainly caused by the working fluid drying up in condensation section. The total thermal resistance is related to many factors, such as the thermal conductivity of tube-shell material, wall thickness, wick thickness, the number of the grooves, the lengths of condensation and evaporation sections, the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with trapezium-grooved wick should be rationally designed according to specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements and be in the optimal state.

The paper presents the preliminary design of the special heat exchanger. The device under consideration is the kind of immersed coil heat exchangers. It consists of three vertical coils: two coils are standard, water is used as a heating medium; one coil is filled by the refrigerant R134a which transfers the waste heat from refrigeration and air conditioning system during the boiling processes. In order to prevent the possible refrigerant leakage, the special buffer layer filled with the nanofluid is mounted in the Freon coil. Thermophysical properties of the nanofluid cause the intensification of the heat transfer through the buffer layer and the same increase of the heat transfer rate. Calculations of thermal power were made. Correlations of heat transfer coefficients in curved tubes, pressure drop correlations for flow through helical coil tubes and correlations describing the heat transfer in the buffer layer, were applied. Results of the calculations indicate of the influence of of Freon coil on the exchanger heat transfer rate. Heat power of Freon coil is about 7 – 25% of water coil thermal power. Thus, the waste heat applied significantly increases the exchanger heat transfer rate.

This work deals with heat transfer over heat pipe. In the introduction is knowledge about heat pipes. In the experimental part is influence of working conditions to heat transfer calculations of heat pipes Currently the problem with the increasing number of electronic devices is a problem with the outlet Joule heating. One of more alternatives of outlet joules heating without the using of mechanical equipment is the use of the heat pipe. Heat pipes are easy device to manufacture and maintenance of low input investment cost. The advantage of using the heat pipe is use it in hermetic closed electronic device which is separated exchange of air between the device and the environment. This experiment deals with the influence of changes in the working tube diameter, working position and changing the working medium depending on performance parameters. The result of this paper is finding the optimal working conditions with ideal working substance for the greatest heat transfer for 1cm2 sectional area tube. One of more alternatives using heat pipes is a heat transfer Joule heating without the using of mechanical equipment.

As a novel latent functionally thermal fluid, microcapsulated phase change material slurry (MPCMS) has many potential applications in the fields of energy storage, air-conditioning, refrigeration and heat exchanger, etc. In order to investigate the heat storage and heat transfer performance of MPCMS, natural convection in a rectangular enclosure heated by bundle heat exchanger has been studied numerically in this paper. The effects of mass concentration (Cm) of MPCMS, the vertical spaces of bundle heat exchanger on the natural convective heat transfer are investigated. The results indicate that, MPCMS with Cm=30% shows the best natural convectionperformance, and a lower position of bundle heat exchanger can strengthen the natural convection.

Fixed plate enthalpy heat exchanger which utilizes permeable material as heat and moisture transfer surface has been used as an energy recovery system to recover sensible and latent heat in HVAC systems. The heat exchanger effectiveness is affected by the air flow profile. It is well known that counter flow configuration provides highest effectiveness, however, in real applications, it is not possible to implement a counter flow configuration, as both inlet and outlet ducts of the two flow streams are located on the same side of the heat exchanger. Therefore, several quasi-counter-flow heat exchanger designs including Z-shaped, L-shaped, Z-shaped opposite flow configurations are proposed in this research and their effect on energy consumed by an air conditioning cooling coil has been investigated, where each of the proposed heat exchanger is incorporated in an air conditioning cooling coil model. The modeled cooling coil energy consumption and energy recovered by the heat exchangers are evaluated under Kuala Lumpur weather conditions. It has been found that an air conditioner coupled with L-shaped heat exchanger recorded up to 20% increase in energy recovery in comparison with Z-shaped oposite and Z-shaped heat exchanger.

Improving the performance of the computers and maintaining the operating temperature is an important task for the computer hardware manufacturers. The junction temperature of the electronic components is a critical problem which needs to be addressed in a competent way. Due to the improvement in the technology, the size and weight of the electronic components reduced to a greater extent and which in turn increases the operating power and speed. This increases the heat generated by the electronic component. Electronic components normally use conventional rectangular fin as heat sink for the step up in heat transfer. The need is to make a heat sink design that should overcome the problem related to transfer of heat by the electronic components. The heat transfer depends on parameters like heat sink’s surface area, pitch, design and material used. Optimization of the fin design by number of experiments is more expensive and laborious as well. CFD (Computational Fluid Dynamics) simulation validated with experimentation can be a good alternative for performing series of experiments. CFD modeling and simulation for the best fin design has been carried out for the current study. An alternative design for conventional rectangular fin has been proposed for this study called as Extruded Rectangular Fin (ERF). The proposed ERF shows good heat transfer when compared to conventional and interrupted rectangular fin with holes. Optimum cooling achieved for the system with the fin aspect ratio of 3.5.

The development of heat exchangers from two streams to multi-stream passage arrangement becomes a key problem for heat exchanger design. In this paper, a new design is developed for multi-stream (four-channel) heat exchanger. Multi-channel heat exchangers are extensively used in refrigeration and air conditioning, chemical industries, milk pasteurization, cryogenics industries and energy-recovery applications due to their higher heat transfer rates. The focus of this study is to determine the performance of four-channel counter flow heat exchanger. The hot and cold fluids are assumed to recirculate and exchange heat between them. Finite element model of the heat exchanger is developed based on the detailed geometry and the specific working conditions with the help of which effectiveness of the four-channel heat exchanger is computed. Non-Dimensional parameters are introduced which makes the analysis more versatile. The effectiveness is computed for different values of NTU and heat capacity ratio.

Every technological process developed since the beginning of humanity to the present day always involves some kind of energy use, either mechanical energy of the body or energy from burning fuel or the solar energy obtained from the sun. To manipulate and use that energy, the man always developed resources and equipment to allow it. Among the wide range of equipment, heat exchangers, designed to transfer heat from one fluid to another, will be analyzed in this work. To do this analysis, are used computational fluid dynamics (CFD) techniques to analyze the flow behavior of a compact heat exchanger, of tube and louvered fins type. After this step that aims to pull the parameters of efficiency, optimization features will be used to be able to propose a model for more efficient fin.

This paper compares the transient thermal performance between counter and parallel cross flow heat exchangers subjected to time varying inlet mass flow rates and inlet temperatures that hasn’t been previously discussed in the available literature. Specifically the transient performance of 2 pass and 3 pass cross flow heat exchangers is discussed in this paper. In the present study the energy balance equations for the hot and cold fluids and the heat exchanger wall were solved using an implicit central finite difference method. Representative values of NTU were considered, and the NTU’s of the heat exchanger were assumed to be uniformly distributed among the heat exchanger passes. Other physically significant parameters such as the capacity rate ratio and the convection heat transfer resistance ratio were systematically varied. A detailed summary based on the observations has been presented.

With the rapid development of the national economy, the use of low-temperature heat in thermal power plant boiler can not be ignored.Although low temperature economizer is widely used in low-temperature waste heat recovery of thermal power plant boiler, the problems of corrosion and fouling are very significant.New type PTFE heat exchanger filled with high thermal conductivity properties can replace the existing metal heat exchanger, fundamentally solve the problems of corrosion and fouling, meet the future development of the thermal power plant, and realize the energy recycling to maximize the benefit of energy.

Micro heat pipe is a two-phase heat transfer device offering effective high heat-flux removal in electronics cooling. Essentially, micro heat pipe relies on the phase change processes, namely evaporation and condensation, and the circulation of working fluid to function as heat transfer equipment. The vast applications of micro heat pipe in portable appliances necessitate its functionality under different orientations with respect to gravity. Therefore, its thermal performance is strongly related to its orientation. By incorporating solid wall conduction, together with the continuity, momentum, and energy equations of the working fluid, a mathematical model is developed to investigate the heat and fluid flow characteristics of inclined micro heat pipes. We investigate both the favorable and adverse effects of gravity on the circulation rate which is intimately related to the thermal performance of micro heat pipes. The effects of gravity, through the angle of inclination, on the circulation strength and heat transport capacity are analysed. This study serves as a useful analytical tool in the micro heat pipe design and performance analysis, associated with different inclinations and operating conditions.

This paper presents the heat transfer and friction coefficient correlations for triangular plain fin surfaces of plate fin compact heat exchanger. It will be prohibitively expensive and time consuming to fabricate heat exchanger cores and conduct experiments over reasonable ranges of all the geometric variables. In contrast, it is relatively easy and cost effective to carry out a parametric study through numerical simulation and derive acceptable correlations for use in industry. A numerical model has been developed for the triangular plain fin of plate fin heat exchanger. The CFD analysis is carried out using FLUENT 12.1, Colburn factor j and fanning friction factor f are calculated for different Reynolds numbers. These values are compared with the available literature data of j and f factors. The correlations have been expressed in terms of two separate equations over the low and high Re regions along with dimensionless geometric parameters.

HHeat exchangers have been used since the start of industrialisation, and since then have been modified in a plethora of complex and intricate ways to suit the needs of the corresponding application, but in this paper a simple modification on the existing design has been investigated numerically, which has proven to be effective. A standard tube-in-tube heat exchanger has been modified such that the external tube tapers (converges) to a smaller diameter. The inner tube carries the cold working fluid which absorbs the heat energy carried by the fluid in the outer tube. A numerical simulation has been carried out, taking into account the mass flow rate, fluid temperatures, heat transfer etc., which are governed by fundamental heat transfer equations. The results of the simulation are used to analyse the effect of this modification (convergent tube) on the efficiency of the heat exchanger, which has been found to increase significantly along with the rate of heat transfer.

A numerical investigation has been carried out in the present work to study flow characteristics and thermal performance of a chevron type brazed plate heat exchanger (PHE). A local element-by-element analysis utilizing e-NTU method is employed for simulating the heat exchanger. In this approach, Nusselt number is expressed in terms of friction factor which in turn, is given as a function of chevron angle of the heat exchanger. Water has been used as cold and hot fluid. Effect of fluid flow rate and inlet temperatures on the heat duty, overall heat transfer coefficient, fluid outlet temperatures and pressure drop have been studied. When compared with literature results of intermating plate heat exchangers, chevron type plate heat exchanger gives greater heat transfer enhancement, though with increased pressure drop.

Nanofluids are fluids containing nanometer-sized particles of metals, oxides, carbides, nitrides, or nanotubes. They exhibit enhanced thermal performance when used in a heat exchanger as heat transfer fluids. Alumina (Al2O3) is the most commonly used nanoparticle due to its enhanced thermal conductivity. The work presented here, deals with numerical simulations performed in a tube-in-tube heat exchanger to study and compare flow characteristics and thermal performance of a tube-in-tube heat exchanger using water and Al2O3/water nanofluid. A local element-by-element analysis utilizing e-NTU method is employed for simulating the heat exchanger. Profiles of hot and cooling fluid temperatures, pressure drop, heat transfer rate along the length of the heat exchanger are studied. Results show that heat exchanger with nanofluid gives improved heat transfer rate when compared with water. However, the pressure drop is more, which puts a limit on the operating conditions.

The applications of heat exchangers are vast and the enhancement of heat transfer and compact size are the key factors for designing the heat exchangers in order to achieve energy savings. In the field of tubular heat exchangers one of the possible ways for reducing the space occupied by the exchanger is by bending tube axis in helical shape. This option is particularly suitable when construction simplicity is needed and the geometry of the place in which the exchanger has to be housed is the cylindrical one. In this paper, an attempt is made to enhance the heat transfer rate without application of any external power. This is achieved by providing the helical tube in tubes. The parameters influencing the nature of flow in a helical coil heat exchanger are the tube geometry namely pitch coil diameter, pitch and tube diameter. CFD analysis is carried out to study these geometry effects on heat transfer and hydraulic characteristics by varying Reynolds number (hot fluid). The CFD results of velocity and temperature distribution in the heat exchanger are used to estimate the Nusselt number and heat transfer coefficient. This helps to arrive at an optimum value of Reynolds number and Nusselt number for the corresponding tube-to-coil diameter ratios.

This paper reports the development of a novel solar hybrid desiccant cooling system with heat pipe heat exchanger (HPHE). The aim is to achieve higher efficiency to reduce the use of electricity by utilizing the desiccant dehumidification system to remove latent load, while the vapour-compression and heat pipe heat exchanger meet the sensible load. Novelty comes as the heat pipe heat exchanger in the system operates efficiently without external power. Experimental set-up has been built by combining the rotary desiccant wheel, heat pipe heat exchanger with a compressive cooling system. Tests are carried out at typical operative ranges for air-conditioning applications, specifically for high hot and humid locations in Bangi, Malaysia. Acetone is used as refrigerant in the HPHE. Performance of HPHE are tested and proven to have direct impact on Coefficient of performance (COP). The results shows good performance of heat pipe heat exchanger efficiency with average efficiency and capacity of 0.65 and 2kw respectively. It is found that the hybrid system can achieve a higher energy performance in hot humid regions.

Contribution is aimed on lost heat of plate heat exchangers to surrounding environment. Heat losses to vicinity are insignificant relative to transferred heat flow in the plate heat exchangers. This small part of the lost heat is demonstrated in parametric case study of plate heat exchanger, where is the lost part of heat energy lower than 0.50 % in ordinary cases.

Using heat sink to increase the cooling area is the most familiar and fundamental method in LED heat management technology. We develop a new configuration of finned heat sink for LED lamp. It is a circular cylinder with many plate fins radially arranged on the external surface. There are many straight ducts inside the peripheral wall of the cylinder. These ducts form the chimney effect to enhance the heat transfer. This work experimentally investigated the chimney effect on the heat transfer characteristics of the finned heat sink under the free convection state. The aluminum-alloy plate spreader with two vertical plate fins was selected as the control group. The experimental group was the heat sink having the same configuration of the control group but had a vertical passage within the spreader. The results show that the vertical passage did strengthen 8.3~12.1% free convection performance for the present test heat sink.

This research presents an experimental investigation on the heat transfer performance and pressure drop characteristics of a heat sink with miniature square pin fin structure using nanofluids as coolant. ZnO-water nanofluids with particle concentrations of 0.2, 0.4 and 0.6 vol.% are used as working fluid and then compared with the data for water-cooled heat sink. Heat sink made from aluminum material with dimension around 28 x 33 x 25 mm (width x length x thickness). The heat transfer area and hydraulic diameter of the each flow channel is designed at 1,565 mm2and 1.2 mm respectively. Uniform heat flux at the bottom of heat sink is achieved using an electric heater. The experimental data illustrate that the thermal performance of heat sink using nanofluids as coolant is average 14% higher than that of the water-cooled heat sink. For pressure drop, the data show that the pressure drop of nanofluids is a few percent larger than that of the water-cooled heat sink.

A three-dimensional steady-state laminar flow and heat transfer model for fractal tree-like minichannel heat exchanger is developed.The fluid flow and heat transfer process is studied by CFD software. Because of its symmetric structure, only half body of the heat exchanger is calculated. The fluid-solid coupled method is applied and the hexahedral grid is used on the control volume.The temperature distribution and velocity distribution for different heat flux on top boundary surface are obtained with an inlet hydraulic diameter of 3.2mm.The simulated results show that the fractal tree-like minichannel heat exchanger has good temperature uniformity and small pressure drop.

Recently, variousresearches and developments of heat exchangers with high thermal efficiencyhave been in progress to save energy. Baffles are used as design variables in a way that enhancesheat transfer performance of shell and tube heat exchanger. There have beenvarious of researches and developments in the relations between baffles andheat transfer performance. Existing studies on shell and tube heat exchangersare mainly about heat transfer properties of either segmental type baffles orhelical baffles. However, there is inadequateof study with comparisons between the two types ofbaffles. Thus, this paper aims to research changes in heat transfer properties according to thenumber of segmental and helical baffles. It shows pressure drop, temperaturedifference of inlet and outlet, heating surface area of inner flow region, andheat transfer coefficient in tubes.

The frost is easy produced by the surface of evaporator, when finned tube evaporator works, especially in the low temperature and high humidity conditions. COP, electrical power, cooling capacity and frost quantity have significant differences at the conditions of different temperature and humidity. When air conditioning system is used in different areas, system parameters change greatly, so it is important that the experimental research on the heat exchanger in low temperature conditions. The temperature field of the evaporator is calculated and simulated by software, and the simulation results are analyzed and explained.

The research and development situation of liquid nitrogen coil-wound heat exchanger were discussed in view of heat exchange in gas purification field in petrol-chemical industry. The basic designing methods and the multi-stream heat exchange process were illustrated by the cryogenic and high pressure crossing heat exchange equipments of liquid nitrogen coil-wound heat exchanger with multi-stream and multiphase flow, including Three-stream back-cooling heat exchangerin first stage, Four-stream back-cooling heat exchangerin second stage, Five-stream back-cooling heat exchangerin third stage, Multi-stream main back-coolingcoil-wound heat exchanger etc. A series of coil-wound heat exchangers with different mixed fluids and different applications were described. The winding structure characteristics and the work principles of the spiral pipe bundles were elaborated to give references for the scientific design and calculation of coil-wound heat exchanger in cryogenic field. The important research directions and the critical scientific problems were forecasted.

Changing "high consumption energy, low temperature heat to the indoor, waste heat to the environment", and turning the HVAC harmoniously into the natural ecological cycle, conform to the trend of the development of ecological architecture. Heat pump technology is a way of HVAC energy saving the most practical. Although low heat and cold source of the city sewage is ideal, but the quality is very unstable, can not meet the operation requirements of heat exchange equipment. This paper analyzes the key problems of the sewage side in sewage source heat pump technology application in the present: hair dirt clog sewage heat exchanger; fouling in heat surface reduces the heat transfer performance, and results in large heat-transfer equipment in the practical application. According to the key problems of sewage side, this paper prevents hair clogged with large tube heat exchanger; reduces the fouling thermal resistance, and enhances heat transfer process using the heat exchanging technology of circulating fluidized bed.

This work presents a theoretical and experimental analysis of a heat exchanger assisted by five heat pipes made of copper with a metallic mesh 100 of stainless steel which was used as capillary structure. All heat pipes used water as the working fluid and were designed based on the capillary limit model. The heat pipes were developed and tested under heat loads varying from 20 to 50 W before application into the heat exchanger. The theoretical and experimental results were compared and all heat pipes worked satisfactorily. Thereafter, it is presented the development of heat pipe heat exchanger which was tested under heat loads varying from 100 to 250 W. The highest temperature measured on the external surface of the heat pipes was 90 oC and the heat exchanger thermal efficiency varied from 74 to 80%. It is showed that the use of a stainless steel mesh as a porous wick was proved to work successfully in heat pipes.

The research and development of LNG coil-wound heat exchanger (LCWHE) were discussed in view of the heat exchange in LNG field in petrochemical industry. The basic designing methods and the multi-stream heat exchange processes were illustrated by the cryogenic and high pressure crossing heat exchange equipments of LCWHE with multi-stream and multiphase flow, including Four-stream LCWHE in first stage, Three-stream LCWHE in second stage, Two-stream LCWHE in third stage, Multi-stream main LCWHE etc. A series of LCWHE with different mixed refrigerant and different applications were described. The winding structure characteristics and the working principle of the spiral pipe bundles were elaborated to give a reference for the scientific design and calculation of LCWHE in cryogenic field. The major researched directions and the critical scientific problems were forecasted.

Introduces the technological process of the open heating system with a liquid-phase organic heat transfer fluids heater by analyzing the advantages and disadvantages of preventing heat transfer fluids from oxidation based on expansion pipe with cooling water casing. And it presents two methods to prevent heat transfer fluids from oxidation by arranging directly cooling coils or pulsating heat pipes in the expansion tank; it also provides the schematic diagram of those methods as well as comparatively analyzes their advantages and disadvantages.

This paper presents a heat exchanger of louver baffle, the establishment of a three-dimensional model, research by numerical simulation of flow and heat transfer performance of the heat exchanger baffles different louver angle, and analyzes its local temperature, and evaluated for its overall performance. The results show that louver baffle heat exchanger avoids the existence of traditional segmental baffle heat exchanger problem after baffle local flow dead zone; compared with conventional segmental baffle heat exchanger, louver baffle heat exchanger greatly reduces the heat exchanger shell side pressure drop; louver baffle heat exchanger in the unit pressure drop coefficients are higher than the segmental baffle heat exchanger, and with the baffle plate angle increases, with significant energy savings.

Ceramic plate is a new product in solar heat collecting. However, the heat transfer efficiency of the existing products is low. The optimization of the flow path and structure of solar heat collecting ceramic plate can strengthen the heat transfer greatly. This study aimed to obtain the optimization data of the heat transfer characteristics in order to design more efficient solar collecting system. The internal flow path and structure was modified based on the computational fluid dynamics and numerical heat transfer. The result has proved that the internal flow field was made uniform with little increase of the resistance loss, but achieved more efficiency of the heat transfer.

Based on traditional shell-and-tubeheat exchanger, a new heat exchanger which applies to phase change thermal storage was proposed. The thermal storage process of new heat exchanger and shell-and-tube heat exchanger which use paraffin as phase change material and use water as heat-transfer fluid can be simulated by CFD software, respectively. The changes of liquid fraction and heat flux density along with time have been got by computer stimulation. It can be found that maximum heat flux of the new heat exchanger heating wall is 2.5 times than shell-and-tube heat exchanger, melting time of the new heat exchanger is 5 times than shell-and-tube heat exchanger. From the two aspects, the heat storage effect of new heat exchanger is better than conventional concentric tube heat exchanger.

As technology advancement progressed in this information age or commonly known as digital age, thermal management has equally improved to keep up with demands from the electronic sector. Hence, heat sink study has become more and more prominent. Natural convection holds advantages since it is maintenance free and has zero power consumption. The purpose of this research is to study the heat transfer performance of heat sink with parametric variations of number and height of pin fin at temperature 308K, 323K, 338K, 353K and 368K. In addition, effect of porosity ranges from 0.524 to 0.960 on thermal resistance was investigated as well. Study found that heat transfer coefficient increases as temperature difference between heat sink and ambient increases. Thermal resistance decreases when porosity increases until it reaches the minimum and subsequently increases. The optimum porosity shown in this study is around 88%.

Spiral tube exchanger is one of the most important heat transfer devices among the electric water boilers. In this paper, CFD software is introduced to simulate the process of the flow of the spiral tube exchanger. Cases with different inlet velocities of the cold water have been conducted and results show that, temperature increment of the cold water reaches 38.87 K, 20.21 K and 12.12 K with the inlet velocity of the cold water set as 0.05 m/s, 0.09 m/s and 0.13 m/s respectively.

Recent development of nanotechnology led to the concept of using suspended nanoparticles in the heat transfer fluids to improve the heat transfer properties of the base fluids. The heat transfer enhancement by nanofluids is the significant concerns in the efficiency of domestic water heat exchanger system. A computational investigation of the heat transfer in a domestic water heat exchanger is conducted on the water and water-based nanofluids. Copper (Cu) nanoparticle and Alumina (Al2O3) nanoparticle are selected in the water-based nanofluids. Volume fraction of nanoparticle in the nanofluids is set at 0.5 %, 1.0 %, 1.5 %, 2.0 %, 2.5 %, and 3.0 %. Heat exchanger has been invented for the heat transfer from one medium to another medium in many heat transfer systems. Domestic water heat exchanger can be used in a heat pump domestic water heating system. The density, the thermal conductivity, and the dynamic viscosity of the water base fluid are increased while the specific heat capacity of the water base fluid is reduced with the addition of copper as well as alumina nanoparticle. Addition of copper nanoparticle into the water-based heat transfer fluid significantly increases the domestic hot water temperature. The efficiency of domestic water heat exchanger system is optimum when 1.5 % copper or alumina nanoparticle is added into the water-based heat transfer fluid.

In this paper is study the performance of heat exchangers by using computational analysis method. In past decade’s years, many researchers had discovered that nanofluids have a brilliant efficient in the heat transfer process. They believes that applied the nanofluids in the heat transfer equipment would bring a better enhancement compare with the conventional cooling fluids. In the literature journals, the authors have specified focused on the thermal conductivity, specific heat, density, and viscosity of nanofluids. They believes these are the most significant factors of the working fluids that would influence the efficiency of heat exchanger. In this study, an imitated real-life marine transport used of shell and tube heat exchanger to be analyzed. The shell and tube sides of heat exchanger will be filled with Water or nanofluids and Water or seaWater in respectively. The nanofluids will be assumed as single-phase nanofluids with variant of volume fraction of copper and alumina. The computational result of Water at the shell and tube sides will be used as validation of data compared with the technical performance specification given by the supplier. Further, the efficiency of different volume fraction of nanofluids and the optimum of volume fraction of nanofluids in this system would be discussed in the simulation results.

The air cooled heat exchangers are used on a wide range of automotive, construction, industrial or agriculture applications. As the atmospheric air has the lowest convective heat transfer coefficient it is necessary to use different extended surfaces with different geometries. The need for this type of heat exchanger and the relative limited information in the literature, conducted to a study, done at RAAL S.A. Company in collaboration with University “Politehnica” of Timișoara that focuses on finding the optimum length of the straight section depending on the cooler thickness and wavy fin pitch. In the first step we performed analytical investigations on a multiple number of core thickness dimensions, for 5 mm fin pitch. The optimum length of this straight section is considered the section for which the fins that have the highest area goodness factor (J/f). The above numerical study then was to be confirmed in the second step by real life testing. The scope of this study was to determine a relation that shows the influence of the straight fin section on the thermal and hydraulic performances.

The paper analyzes the possibility of providing heating and hot water for residential buildings using a thermal accumulator that converts solar energy. The accumulator uses the latent thermal energy storage. The phase change material is paraffin wax. The heat transfer inside the thermal accumulator was modeled using Fluent module from Ansys 14.5. The mathematical formulation of the CFD analyses followed the phase change of the wax, the heat transfer inside the accumulator and also the turbulence that occurs in the water pipe. The analysis was done in transient regime to observe the latent heat transfer that goes from the molten paraffin wax to the flowing water.

This article is devoted to the complex research method based on mathematical modeling and visualization of thermal fields, which allowed one to obtain the optimal parameters of heat transfer elements of the spacecraft systems of air heating of buildings.

In the past few decades heat exchangers, especially air cooled ones, have become very important equipment in different fields of industry. This led to an active research in finding ways to reduce their overall size and costs. A very important role played in reducing the size of the heat exchanger is the convection capability of air, by being the lowest one, dictates the overall size of the heat exchanger. For this reason we are forced to use extended heat transfer surfaces on the air size. The geometry of such extended surfaces has a high impact on heat and pressure drop performances. The present paper focuses on a study, conducted at RAAL S.A. with the support of University “Politehnica” of Timișoara, to find the influence of the corrugation amplitude of a special kind of extended surface named wavy fin, in the overall performances of a heat exchangers by means of area goodness factor (j/f). Designing and building the different geometries needed in the study will be overkill for the company so we have decided to conduct this study with the help of CFD simulations. In order for this to work we will validate the numerical model with the help of a single experimental test, reducing the time and cost of the entire study. These results are afterwards used to modify the fin’s design to obtain an optimum one.

Utilization of alternative fuels and utilization of waste heat has also become a major research area. This study reports on an investigation on a development of an energy converter of heat engine that converts energy from a waste heat flow process into acoustic power. The energy power converter operates with a temperature gradient imposed on a Celcor ceramic stack which then induces pressure oscillations. The system consists of a simple stainless steel pipe tube with a range of diameter open at one end. A waste heat gas is used to model a potential heat source from automobile engine. A two heat exchanger is required while copper plates are used as the ambient heat exchanger and hot heat exchanger. Effects on pressure oscillations have been observed with a calculated heat rate of 50 W at the stack. The system which operates at atmospheric pressure with air as the working fluid indicates a potential in utilizing the heat produced from waste heat automobile engine into making a new energy resource.

In the context of a constant demand of more compact and efficient heat exchangers, the need for thoroughly researching the influence of the construction parameters impact on heat exchanger's performances arises. The purpose of the paper is to present the numerical results of such a research, carried out at RAAL S.A. with the support of "Politehnica" University of Timişoara. The research consists of assessing the effects of the geometric characteristics, the height in particular, of the inlet and outlet tanks of a water cooler on overall pressure drop, through Computational Fluid Dynamics. The structural complexity of heat exchangers demands that the analysis be divided into multiple, less complex models, in order to achieve accurate and truthful results within a reasonable amount of time and use of computational resources. The paper also focuses on developing a viable method for accomplishing numerical analyses on heat exchangers' parameters.

A technology for using petroleum deposit’s energy and the principle of medium’s phase change heat transfer to make hollow rod into heat pipe, which transferred heat from bottom to top in wellbore by using it without extra energy is proposed. It can improve the temprature distribution of the fluid at the upper part of wellbore; therefore paraffin deposition and flocculation are improved. In this paper, heat transfer model of liquid film and liquid pool is established by means of the equation of N-S.Based on the principle of micro unit in liquid film’s thermal equilibrium and liquid pool’s heat transfer.By analying the heat transfer coeffcients of this two part,it was found out that gravity heat pipe had better heat transfer performance with increasing the length of liquid film in evaporator,improving the flow rate of inner steam and strengthening nucleate boiling of liquid pool,when the requirement of the continuous circulation of two-phase flow was achieved.

For the low temperature waste heat recovery problem, waste heat recycling system was designed based on the heat pipe heat transfer technology of hydrogen in industry. The system is mainly in the process of hydrogen production by methanol steam reforming, using heat pipe excellent thermal conductivity, isothermal and thermal response characteristics, it will be in the low temperature waste heat of flue gas as heat source, in the heat pipe under the action of high efficiency heat transfer, through technology improvement, structure optimization design, achieved high efficiency, energy saved heat transfer to the methanol in the reaction system of hydrogen production, achieved the goal of remaining heat to be recycled.

The medium temperature heat pipe is a highly effective heat transfer element through heat exchange due to phase change of the liquid organic working fluid. A medium temperature heat pipe used in solar energy receiver of parabolic trough thermal power generating system has been analysed, and a medium temperature heat pipe with liquid organic working fluid has been designed. The isothermal performance and heat transfer performance of the medium temperature heat pipe with liquid organic working fluid have been tested under various power input and different inclined angles. Test proves that axial temperature difference of half circle heated medium temperature heat pipe is smaller, and the half circle heated heat pipe with inclined angle is 4°and 8°can work stably, having good axial isothermal performance and heat transfer performance, the influence on isothermal performance and heat transfer performance of the medium temperature heat pipe can be neglected.

This contribution is focused on heat exchangers and their heat losses dispersed into vicinity. In the introduction of the contribution this loss heat flow of heat exchangers is analysed into basic physical processes and with applying simplifying assumptions it is described by a computational equation suitable for technical practice. The result of the study is the confirmation of the general fact that the quotient of losses heat into vicinity with regard to the transferred heat flows in the heat exchanger is insignificant.

A heat sink is a kind of heat exchanger that cools a device by dissipating heat into the environment. The design of heat sink by numerical simulation depends to a large extent upon boundary condition between the heat sink and its surroundings. The boundary condition is usually defined by Heat Transfer Coefficient (HTC) which can be used to measure heat resistance between heat sink and surrounding. Determination of HTC is a difficult problem, depending on many factors such as air velocity, material properties, shape of radiators and surface treatment, etc. A new simple reverse method has been suggested in the present work. The reverse method is suggested according to Mean-Value Theorem in mathematics. By comparing the temperature curves between simulation and real measurement, the temperature differences can be minimized by selecting different HTCs.

Heat pipe has excellent conductivity of heat and diversity of structure, so it can be used in machining which can decrease or avoid using the cutting fluid. In this paper, the abrasive tool with rotating heat pipe was designed. To validate that the abrasive tool with heat pipe can safely and steadily grind materials, the structure of abrasive tool was finite element analyzed which included static analysis. Furthermore, the heat transfer performance of heat pipe was tested. The results indicated that heat pipe has certain cooling impacts relative to no heat pipe in machining.