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Experimental investigation of heat transfer effectiveness on finned-tube thermoacoustic heat exchanger

Experimental investigation of heat transfer effectiveness on finned-tube thermoacoustic heat exchanger

The heat transfer performance of heat exchangers in an oscillatory flow has been investigated by a number of researchers. Garrett [1] described the design and fabrication technique of heat exchanger for using in thermoacoustic devices. A couple of fin and tube heat exchangers were made and their performance was predicted. The convective heat transfer coefficient of heat exchangers was estimated using Blasius-Pohlhausen model for laminar flow. The results showed that the performance was in excellent agreement with the model. However, the comparison of convective heat transfer between the model and measurement was shown in limited testing conditions. The influences of parameters that may affect the heat transfer performance were not demonstrated. It was suggested that the heat exchanger performance could be improved if material of high thermal conductivity and more sophisticated fabrication technique are used.
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Evaluation of heat exchanger on thermoacoustic performance

Evaluation of heat exchanger on thermoacoustic performance

Heat exchangers for thermoacoustic devices are different from traditional ones in several key features. First of all, heat transfer in the thermoacoustic working fluid takes place in oscillating flow characterized by zero mean and very low instantaneous velocity, characterized by a tidal displacement (TD) of the order of several millimeters. Convective heat transfer coefficients on the surfaces of the heat exchangers, essential parameters in heat exchanger design, cannot be predicted for oscillating flow based on methods for unidirectional flows because of the very complex features of oscillating flow and geometries. Experimental data regarding convective heat transfer coefficients are available for a few special conditions and combinations of parameters only (Ishikawa, 1999). Furthermore, the heat exchanger performance depends on numerous geometrical, thermophysical and operational parameters (dependent on the oscillation frequency). Therefore, conventional heat exchanger design methods, such as the logarithmic mean temperature difference (LMTD) or the effectiveness-number of transfer units (e-NTU) method, cannot be applied directly to the design and sizing of heat exchangers for thermoacoustic devices (Cila Herman and Yuwen Chen, 2006)
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Performance of finned tube heat exchanger – Review

Performance of finned tube heat exchanger – Review

IJEDR1601029 International Journal of Engineering Development and Research (www.ijedr.org) 164 transverse to the main-flow direction (x). In this case the cross-flowing fluid temperature varies with x and y. In contrast, for the unfinned tube bundle of Fig.3.b, fluid motion, hence mixing, in the transverse direction is possible, and temperature variations are primarily in the main-flow direction. Since the tube flow is unmixed in either heat exchanger, both fluids are unmixed in the finned exchanger, while the cross-flowing fluid is mixed and the tube fluid is unmixed in the unfinned exchanger. The nature of the mixing condition influences heat exchanger performance.
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Online Full Text

Online Full Text

The heat transfer performance of heat exchangers in an oscillatory flow has been investigated by a number of researchers. Garrett [1] described the design and fabrication technique of heat exchanger for using in thermoacoustic devices. A couple of fin and tube heat exchangers were made and their performance was predicted. The convective heat transfer coefficient of heat exchangers was estimated using Blasius-Pohlhausen model for laminar flow. The results showed that the performance was in excellent agreement with the model. However, the comparison of convective heat transfer between the model and measurement was shown in limited testing conditions. The influences of parameters that may affect the heat transfer performance were not demonstrated. It was suggested that the heat exchanger performance could be improved if material of high thermal conductivity and more sophisticated fabrication technique are used.
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Investigation of Effective Parameters on a Thermal Load in a Thermo-Acoustic Refrigerator

Investigation of Effective Parameters on a Thermal Load in a Thermo-Acoustic Refrigerator

ABSTRACT: This article aims to inve st igate the effects of various parameters on the thermal load. The governing equations include continuity and Navier- St okes equations for the flow field and the energy equation for the temperature di st ribution in transient mode. Numerical simulation of the thermo- acou st ic refrigerator by taking the non-zero thickness of the plate st ack into account, that is a conjugate heat transfer problem, in a form of 2D has been performed in FLUENT software. Real simulation of thermoacou st ic refrigerators needs a consideration of both heat exchangers, whereas in mo st simulations one or both heat exchangers have been neglected. Results are influenced by the st eady st ate. Input dynamic pressure should be adju st ed according to the temperature of the heat exchanger. The results demon st rate the effect of the di st ance of the plates on the average thermal load sugge st ing that the di st ance between the plates should be four times of the thickness of the plates so that the device works properly. By increasing the di st ance of the plates thermal load decreases. This is mainly because of pressure amplitude reduction induced by an increase in the di st ance between the plates.
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IMPROVING ENGINE OIL COOLING PERFORMANCE FOR VEHICLE USAGE

IMPROVING ENGINE OIL COOLING PERFORMANCE FOR VEHICLE USAGE

This article provides the means of improving engine oil cooling systems in automobiles. The need for the improvement arises due to the frequent breaking down of automobiles as a result of congestion, temperature and nature of the Nigerian roads. In automobiles, the engine is either cooled by air using oil to air heat exchanger or by water using oil to water systems. For the engine to be cooled by air there must be sufficient air flow obtained at high speed. In order to provide solution to this problem, other method of cooling has to be used. Larger plate heat exchanger, Copper as heat exchanger material, additional radiator (oil to air) and a separate cooling circuit (water to air) were the examined factors adding to the cooling performance of the engine oil. Results from the simulation of this methods using Gamma Technology Suite (GTS) software shows that heat transfer rate above 26kW is achieved using any of the four methods. In the cause of this work, only the cooling system was considered.
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Numerical Analysis and Optimization Method to Enhance the Performance of Heat Exchanger used in Rankine Cycle Rajni Kant Kumar 1, Dr. Ajay Singh2 , Prof. Ashish Verma 3

Numerical Analysis and Optimization Method to Enhance the Performance of Heat Exchanger used in Rankine Cycle Rajni Kant Kumar 1, Dr. Ajay Singh2 , Prof. Ashish Verma 3

Heat exchanger is a device which is mostly used in equipment to transfer heat between two process streams which may be in direct contact or may flow separately in channels or tubes [1]. We find numerous applications and one can realize their usage that any process which involves cooling, heating, condensation, boiling or evaporation will require a heat exchanger for these purposes [4]. Similarly the heat exchangers used in automobile industries are in the form of radiators and oil coolers in engines [3]. Heat exchangers are also used in large scale in chemical and process industries for transferring the heat between two fluids which are at a single or two states [2].
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A Design of Compact and Enhanced Heat Exchanger Used in Integrated Nuclear Reactor

A Design of Compact and Enhanced Heat Exchanger Used in Integrated Nuclear Reactor

Thermal-hydraulic characteristics and design methods of a compact and enhanced heat exchanger are presented in this paper. The heat exchanger was designed with concentric double-pipe of double-side heat transfer and annular flow channel, which possesses more than 2 times as much density of heat transfer surface as that of ordinary tubular heat exchangers and lower pressure drop in primary side. This type of heat exchanger is especially suitable for application in the integrated nuclear reactor with natural circulation in primary circuit. Keywords: Concentric Double-pipe, Compact and Enhanced, Heat Exchanger, Integrated Nuclear Reactor.
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An Investigation into the Effect of Porous Medium on Performance of Heat Exchanger

An Investigation into the Effect of Porous Medium on Performance of Heat Exchanger

Recent advances in high-technology fields such as elec- tronic system have lead to dramatic increases in heat flux levels, for thermal management of such systems, more efficient heat transfer enhancement techniques are being explored. There has been a growing interest in heat transfer enhancement using a porous medium and several studies have reported that the use of porous medium for heat transfer yields higher heat transfer performance than existing techniques such an pinned-fin array or twisted tape inserts. Hunt and Tien [1] experimentally studies forced convection through a fibrous medium and showed that with high permeability porous materials, heat trans- fer enhancement of up to four times higher than without the porous medium could be achieved mainly due to higher thermal dispersion effects. Kuzay [2] investigated heat transfer enhancement using metal-wool filled tubes. Hwang and Chao [3] conducted experiments and nu- merical simulation for the heat transfer behavior of sin- tered metallic materials. Hadim [4] considered discrete porous bands in a channel with discrete heat source on one wall. Vafai [5] considered discrete porous blocks on one wall of a rectangular channel. These studies demon- strated that with proper selections of governing parame- ters and different geometric structures of porous medium,
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NUMERICAL INVESTIGATIONS ON HEAT TRANSFER AND FLOW STRUCTURE IN A CIRCULAR TUBE WITH VARIOUS SHAPES OF WINGLET VORTEX GENERATORS

NUMERICAL INVESTIGATIONS ON HEAT TRANSFER AND FLOW STRUCTURE IN A CIRCULAR TUBE WITH VARIOUS SHAPES OF WINGLET VORTEX GENERATORS

Figs. 8a, b and c illustrate the tangential velocity vectors in transverse planes at various x/D values for the RWVG, DWVG and CWVG at BR = 0.2, Re = 1000 and upstream case, respectively. The similar flow pattern as downstream is found in upstream case, but the rotational direction is in reverse (see Fig. 10). The counter rotating vortex flow with common-flow-down is found in upstream case when considering at the upper pair of the vortex flow. The CWVG gives the highest density of the tangential velocity vectors, while the DWVG performs the lowest values. The details of the tangential velocity vectors in transverse planes at various x/D values: 0.25, 2.75, 5.25, 7.75 and 10.25, for downstream and upstream are presented in the Figs. 9a and b, respectively. The counter rotating vortex flow and impinging flow on tube wall for both downstream and upstream cases lead to a better fluid mixing between the core of the flow and close to the wall regime. The better fluid mixing and impinging flows are keys for heat transfer augmentation and performance enhancement.
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HUMAN CALORIMETER FOR DIRECT AND INDIRECT MEASUREMENT OF 24H ENERGY-EXPENDITURE

HUMAN CALORIMETER FOR DIRECT AND INDIRECT MEASUREMENT OF 24H ENERGY-EXPENDITURE

Sensible heat loss was measured using a water-cooled heat exchanger, and the temperature of water entering the heat exchanger was controlled to maintain a mean temperature [r]

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Performance Analysis in Cross Flow Plate Fin Type Heat Exchanger

Performance Analysis in Cross Flow Plate Fin Type Heat Exchanger

Figure 2 to 18 .shows plot between Nusselt Number experimental vs Reynolds Number for base fluid-water system, 0.01%nanofluid system, 0.05% nanofluid system for parallel and counter flow. It clearly shows that Sodium Alginate has higher Nusselt Number for a particular Reynolds Number compared to CMC. For Water-SA system system as Reynolds number decreases with individual heat transfer coefficient, also decreases for (hot side) and Reynolds Number increases with individual heat transfer coefficient also increases for (cold side).

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The Efficiency Analysis of the Exhaust  Air Heat Pump System

The Efficiency Analysis of the Exhaust Air Heat Pump System

When installing the exhaust air heat pump system in an old building, pre-conditions have to be met, without which it is not possible to ensure effective work of the system and indoor climate that satisfies requirements. The heating system of the building has to be adjusted to a low temperature heating graph, the recommended graphs are 55/40 or up to 60/40, because the heat pump works more effectively at a low temperature. There should be no towel dryers before the water extraction devices in the domestic hot water system, so that the hot water temperature would not have to be higher than 55 ˚C. The consumption analysis performed during a year showed that the exhaust air heat pump is able to produce heat according to the amount of exhaust air flow in these conditions (the air flow rate, indoor air temperature, heat transfer, efficiency of the device) producing heat pursuant to the amount of the exhaust air flow. The use of the exhaust air heat pump is more effective if, in addi- tion to granting heat energy to the heating system, it can also be used for producing domestic hot water. In apartment buildings with the conventional mechanical exhaust ventilation system, the indoor climate is good. However, studies show that in those apartment buildings it is reasonable to use the exhaust air heat pump for energy conservation.
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Evaluation Performance Of Louvered-Fin Compact Heat Exchanger

Evaluation Performance Of Louvered-Fin Compact Heat Exchanger

When this louvered fin was firstly introduced, it was believed that increased heat transfer was due to added turbulence initiated by flow through the louvered array [3]. But this theory was later proved wrong by the visualization studies on scaled up louver design [3]. It was observed that as air passes through the louver, the flow resulted in two distinct flow directions to be classified: axial (or duct) directed flow and louver flow. Axial flow occurs when the flow maintains the directions of the inlet flow. Louver directed flow occurs when the flow was aligned parallel to the louver [3]. Figure 2.5 shows clearly the two directions indicated in the louvered fin cross section.
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An Optimized Plate Fin Type Heat Exchanger Pandey Mukesh Kumar, A.E. MPPGCL, India Gaur Anurag, A.E. MPPGCL, India

An Optimized Plate Fin Type Heat Exchanger Pandey Mukesh Kumar, A.E. MPPGCL, India Gaur Anurag, A.E. MPPGCL, India

Abstract:- Heat exchangers are one of the vital components in diverse engineering plants and systems. So the design and construction of heat exchangers is often vital for the proper functioning of such systems. It has been shown in [Barron, 1985] that the low temperature plants based on Linde – Hampson cycle cease to produce liquid if the effectiveness of the heat exchanger is below 86.9%. On the other hand in aircrafts and automobiles, for a given heat duty, the volume and weight of the heat exchangers should be as minimum as possible.
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Heat-Pipe Heat Exchanger

Heat-Pipe Heat Exchanger

The heat exchanger is consisted of casing, heat transfer bundle, the partitions of cold and hot sides, and the middle partition. The casing is divided into two regions by the middle partition, namely the cold stream passage and the hot stream passage. The heat transfer bundle is fixed on these three partitions. The heat transfer bundle located in the hot stream passage is the hot end while the heat pipe bundle in the cold stream passage is the cold end. The hot stream is the flue gas and the cold stream is the fresh air.

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An Investigation of Indirect Evaporative Coolers, IEC With Respect to Thermal Comfort Criteria

An Investigation of Indirect Evaporative Coolers, IEC With Respect to Thermal Comfort Criteria

consumes a small amount of electricity for fan and water pump. Ren and Yang [9] developed an analytical model for the coupled heat and mass transfer processes under real operating conditions with parallel counter-flow configurations. Conventionally, one-dimensional differential equations were used to describe the heat and mass transfer processes. In modeling, values of Lewis number and surface wettability were not necessarily specified as unity. Effects of spray water evaporation, spray water temperature variation and spray water enthalpy change along the heat exchanger surface were also considered in model equations. Hettiarachchi et al. [10] investigated the effect of the longitudinal heat conduction in the exchanger wall of a compact-plate cross flow IEC with the NTU method numerically. The results of this research showed that the thermal performance deterioration of evaporative coolers may become significant for some typical operating conditions and could be as high as 10%, while it lies at less than 5% for most conservative conditions. Martin [11] studied heat recovery with a semi-indirect evaporative cooler by the experimental design method. The results showed that for low relative humidity contents and high temperatures of air supply, the main effect is evaporative from the surface of the ceramic pipes. For high temperatures and relative humidity of the air supply, dehumidification takes place and thus condensation appears in the exterior surface of the pipes and the latent and sensible heat recovered are added. A possible use of this recovery system can be in climates with high temperatures and humidity, such as tropical environments where the system could reduce the humidity of the primary air supply by using the cooling power of the secondary air.
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The Influencing Factors Analysis of Heat Exchanger in Engineering Practice

The Influencing Factors Analysis of Heat Exchanger in Engineering Practice

The model in this paper, air import and export is simplified to a rectangle, in order to facilitate the convergence, extend the length of export appropriately, only take a heat transfer characteristic lengthways, which contains a row of pipe and the surrounding smoke and air, the picture 2 is the flow field chart of smoke passageway’s cross section. Divide into two sections breadthwise, do analog computation respectively, but it need to do a experiment to let the parameter of two connection parts to be same mainly. The picture 3 is the left model and left grid model(left model after divided grid, the node number is 739481, the grid number is 2007070.), the parameters of left model’s air inlet and smoke outlet is corresponding to the parameters of right model’s air outlet and smoke inlet. The compute mode of right model is similar to the left model, we only go into detail with left for example.As shown in picture 4 is the end view of no plug-in model and plug-in model. External is smoke passageway, the middle is heat exchange tube, the internal is air passageway, exchanging heat for fair current.
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Numerical and experimental optimisation of a high performance heat exchanger

Numerical and experimental optimisation of a high performance heat exchanger

The aim o f this research is to numerically and experimentally scrutinise the thermal performance o f a typical heat exchanger fitted in a domestic condensing boiler. The optimisation process considered the pins' geometry (circular pins and elliptical pins), pins' spacing, pitch distance, the pressure drop across the heat chamber and the occurrence of thermal hot spots. The first part o f the study focused on the effect o f altering the circular pins spacing and pins pitch distance o f the heat exchanger. .Computational Fluid Dynamics (CFD) is used to scrutinise the thermal performance and the air flow properties o f each model by changing these two parameters. In total, 13 circular pin models were investigated. Numerical modelling was used to analyse the performance o f each model in three- dimensional computational domain. For comparison, all models shared similar boundary conditions and maintained the same pin height o f 35 mm and pin diameter o f 8 mm. The results showed that at a given flow rate, the total heat transfer rate is more sensitive to a change in the pins spacing than a change of the pins pitch. The results also showed that an optimum spacing o f circular pins can increase the heat transfer rate by up to 10%.
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HYBRID AIR CONDITIONING FOR BETTER ENERGY ECONOMIC CONSUMPTION

HYBRID AIR CONDITIONING FOR BETTER ENERGY ECONOMIC CONSUMPTION

414 | P a g e In the present age with depleting sources of energy there is always a target to get the best energy ratios so that there will be minimum electric power consumption in operation of the air conditioning units. Many methods and ideas from evaporative cooling, thermoelectric cooling etc have been tried to keep the electricity consumption to a minimum in air conditioning applications. Individually these ideas do not stand good but by combination of two or more concepts in a collaborative manner stands a possibility to develop an energy efficient method of air conditioning. Thus there is a proposal to use the conventional vapor compression cycle in conjunction to thermoelectric cooling and earth heat exchanger technique to reduce the power consumption of the air conditioner and thereby increase the COP of system.
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