Heat Transfer

Automotive car radiator is a heat exchanger and its basic principle is to transfer heat between one medium to another. Heat exchanger is used to perform this kind of work from one side of a fluid to another without mixing them. It maximizes the use of surface area in order to get a higher rate of heat transfer between the systems. Nowadays, automotive radiator has some problems to deal with and the major problem is high demand in terms of enhancement of heat dissipation especially for advanced engines that are built in compact size. Most of the energy produced by the engine is lost due to combustion and it causes the engine to experience overheating. Overheating will lead to failure of the system such as wear formation between engine, metal damage of inner parts and inefficient lubricating process. A new generation of automotive heat exchanger must be able to perform high level of heat transfer while maintaining its compact and advanced design.

In this paper two-phase flow heat transfer of liquid nitrogen is investigated using ANSYS CXF module. The plotted results shows temperature variation representing the calculative result profiles. The mass density gradient plot also represents density variation in terms of vector density change. Simulation results differing from the data but shows same trend with it which can be improved with more physics considerations.

Abstract. Experimental and numerical simulation of heat transfer and flow regimes for vertical flow across horizontal tubes are presented for mass flow rate in the range 0.03 – 0.17 kg/s and heat fluxes in the range 1.07–1.35 kW/m 2 . The tubes had a diameter of 9.75 mm and a pitch to diameter ratio of 1.85. The CFX version 14.0 from ANSYS was used to predict the flow regimes and the temperature distribution in the tube bundles. These data and the predictions from numerical simulation were compared with the data available in the literature. It is found that the circulation zone in the shell becomes bigger as the mass flow rate is increases. The flow patterns identified in this experiment are bubbly, intermittent and annular flow. These data agrees well with the published data.

transfer and friction characteristics for water, ethylene glycol and ISOVG46 turbine oil flowing inside four tubes with three dimensional internal extended surfaces and copper continuous or segmented twisted tape inserts within Prandtl number range from 5.5 to 590 and Reynolds numbers from 80 to 50,000. They found that for laminar flow of VG46 turbine oil, the average Stanton number could be enhanced up to 5.8times with friction factor increase of 6.5fold compared to plain tube. Betul Ayhan Sarac (Betul Ayhan Sarac et al., 2007)[29] conducted experiments to investigate heat transfer and pressure drop characteristics of a decaying swirl flow by the insertion of vortex generators in a horizontal pipe at Reynolds numbers ranging from 5000 to 30000. They observed that the Nusselt number increases ranging from 18% to 163% compared to smooth pipe. Experimental investigation on heat transfer and friction factor characteristics of circular tube fitted with right-left helical screw inserts of equal length and unequal length of different twist ratios was done by (Sivashanmugam et al., 2007)[30]. They observed that heat transfer coefficient enhancement for right left helical screw inserts is higher than that for straight helical twist for a given twist ratio. A maximum performance ratio of 2.97 was obtained by helical screw inserts. Heat transfer, friction factor and enhancement efficiency characteristics in a circular tube fitted with conical ring twisted tubes and a twisted-tape swirl generator were investigated experimentally by Promvonge (Promvonge et al., 2007)[31]. Air was used as test fluid. Reynolds number varied from 6000 to 26000. The average heat transfer rates from using both the conical-ring and twisted tape for twist ratios 3.75 and 7.5, respectively are found to be 367% and 350% over the plain tube. The effect of two tube insert wire coil and wire mesh on the heat transfer enhancement, pressure drop and mineral salts fouling mitigation in tube of a heat

In last few years so many research have been done for enhancing the heat transfer rate like inserting baffles, twisted tapes, brushes, etc. This leads to increase in weight of heat exchangers and also cost of manufacturing. The world wide researchers are making hard efforts to find out suitable alternatives for heat exchangers with different geometry and varying parameters which effects on performance of heat exchanger. Now days nanofluid has became blessings for researchers. Nanofluid increases the heat transfer rate when suspended in base fluids water, ethylene glycol. With the fast track development of nanotechnology, particles of nanometer size are used for

Heat Sinks are an extremely useful component used to lower the maximum temperature of various electronic devices during operation so as to increase their thermal efficiency and performance. Fins constitute an important and integral component of sinks. It is a passive cooling technique. Plate fin heat sinks are used in varied applications owing to its low manufacturing cost, ease of manufacture and its economical way to dissipate unwanted heat. Steady state natural convection is experimentally investigated for 03 sets of vertically mounted fin heat sinks.Aluminium is used because of its high conductivity. Length and fin thickness is kept constant at 100 mm and 05 mm respectively. Fin height is successively increased as 05mm, 15mm, 25mm.Aspect Ratio for above three sets is thus 0.05, 0.15 and 0.25 respectively. Effect of varying height, heat input and aspect ratio, keeping length constant is investigated on heat transfer through the sinks.

Sihu Hong et.al.[10] have been worked on Experiment study on heat transfer capability of an innovative gravity assisted ultra-thin looped heat pipe. In this present work they have introduced a kind of gravity assisted ultra- thin looped heat pipe (ULHP) with 1.5 mm thick wickless flat evaporator that can be applied for power battery thermal management system, and investigated the heat transfer capability of the ULHP. Air cooling was used as the condensation method considering its advantage of low price and wide application in all walks of life. A series of experiments were conducted under different condensation powers during the same heating load range which started from 20 W to 80 W, to find out the best condensation condition of the ULHP. The experiment results indicated that the ULHP can work most effectively as the fan voltage was 9 V, under which the ULHP can start up at minimum heat flux of 0.22 W/cm2, with the start-up temperature of 47 °C, and the minimum thermal resistance was just 0.097 W/K during the heat load range from 20 W to120 W.

Energy saving is very important in our global world, heat exchanger is useful for energy saving.Spiral heat exchangers play a main role in cooling high density and viscous fluids. Spiral heat exchanger has excellent heat exchange because of far compact and high heat transfer efficiency. Spiral heat exchangers consist of two long plates rolled together forming a spiral. The space between the plates is kept by welding to form the channels for the flow of the fluids. Spiral heat exchanger is self cleaning equipment with low fouling, easily accessible for inspection or mechanical cleaning and with less space requirements.

In order to increase the heat transfer rate of the vapor condensation heat exchanger, the current investigation focused on the condensation heat transfer and forced convection. To increase the heat transfer coefficient, the elliptical pin fins with nanofluid was investigated. The forced convective heat transfer on nanofluids in an elliptical pin-fin heat sink of two different pin orientations was studied by using a finite volume method. With increasing Reynolds number, the recirculation zones behind the pins increased. There were more recirculation zones for the pins with different angular orientations than for pins with the same angular orientation. It was observed that the Nusselt number for the pins with different angular orientations was higher than that for pins with the same angular orientation. The results showed that with increasing volume fraction of nanoparticles and angular orientation of pins for a given Reynolds number, Euler and Nusselt numbers as well as overall heat transfer efficiency increase. By utilizing thin film evaporation in the two-phase flow heat exchanger, investigations were performed for heat flux and pressure distributions. The maximum liquid pressure difference continuously increases with the superheat. The maximum liquid pressure difference peaks at about 5 C superheat. The curvature and interface temperature profiles were different at different superheats. A decrease in temperature occurred when the thin film profile increased in thickness. Both the x and y dimensionless coordinates and superheat at various thin film profiles were viewed and there were two crests in regions  x   4.0, y   0.5  and  x   2.0, y   1.5  , and two shallow troughs in

Considered in the present publication is heat transfer in the coke cooling process as a factor defining the ETB vertical dimensions. The coal blend heating chamber provides an opportunity to intensify heat exchange, in particular at the expense of counter-flow of cold (280˚C) coke-oven gas present in the flue of a coke-oven battery. This method was patented by the author in co-authorship with V.M. Ljapunov [5]. However use of the same gas in a coke cooling chamber is problematic, first, because of the impermeable solid bed used in this camera, secondly, because of potential ability of such gas being taken aside from the chamber top part to exert negative influence on the quality of coke leaving the ETB, and thirdly, due to danger of deteriorating the environment near the ETB. The presence of high CO concentration in the atmosphere in the vicinity of the USTK (Coke Dry Cooling Plant) utilizing coke-oven gas was proved.

Thermal analysis is to determine heat flux and temperature distribution by with different aluminum alloys (\aluminum alloy, 7075). By observing the CFD Analysis the heat transfer rate and mass flow rate are increases by increasing the Reynolds number and more heat transfer rate for pitch2 mm and height 24mm heat sink.By observing the thermal analysis the heat flux value more for aluminum alloy 7075 material. So we conclude the aluminum alloy 7075 material is better for heat sink.

This paper describes the construction of an algorithm for conjugate heat-transfer calculations in order to find the most suitable form for the heat sink of an electronic chip. Applying volume averaging theory (VAT) to a system of transport equations, a heat-sink structure was modeled as a homogeneous porous medium. The geometry of the simulation domain and the boundary conditions followed the experimental set- up used in the Morrin-Martinelli-Gier Memorial Heat Transfer Laboratory at the University of California, Los Angeles. The example numerical simulations were performed for the test section with an isothermal structure as well as for the heat-conducting aluminum pin-fins. A comparison of the whole-section drag coefficient C d as a function of Reynolds number Re h reveals good agreement with existing data, whereas the

and removes the heat from the electronic devices. Heat pipe is a very important device to transfer the large quantities of heat through a small area with small temperature difference.Heat pipes are very frequently used in the space applications. The main characteristic of heat pipe is, heat pipe works in the absence of gravity also and liquid flow does not depend on gravity. Heat pipe has ability of accepting the heat in non- uniformly manner. Heat pipe is a very simple mechanical device and it has no moving parts. Heat pipe is a simple device it makes the change of phase heat transfer. Heat pipe works in the absence of gravity of also. The heat pipe is very much useful in branches of Electronics, Air-conditioning systems, I.C Engines, Gas turbines and Building industries. Heat pipe is an ideal device for removing heat from either a concentrated heat source or from a low temperature heat source. This is the salient feature of heat pipe and this feature is very much useful in the space applications. Heat pipe has a circular cross section and it has a layer of wicking material covered at the inner

Katti and Prabhu [4] measured the jet impinging per- pendicularly the target plate (80×160 mm) made of stain- less steel foil with thickness 0.06 mm. Air was supplied by an compressor through a calibrated orifice flow meter and was cooled to the required temperature. The target plate was heated by ohmic heating and thanks to the low thick- ness the lateral conduction was neglected. The tempera- ture field was measured with IR camera positioned on the other side of target plate. The heat transfer coefficients were established from the temperature time response.

show a drastic increase in heat transfer enhancement. When solid nano particles of high thermal conductivity are added to the base fluid of poor conductivity the resultant properties of the nanofluid have to be established either theoretically or experimentally, so that overall performance of the heat exchanger can be evaluated. Here in this paper the nanofluids related to heat transfer augmentation are discussed. The increases in effective thermal conductivity are important in improving the heat transfer behavior of fluids. A number of other variables also play key roles. For example, the heat transfer coefficient for forced convection in tubes depends on many physical quantities related to the fluid or the geometry of the system through which the fluid is flowing. These quantities include intrinsic properties of the fluid such as its thermal conductivity, specific heat, density, and viscosity, along with extrinsic system parameters such as tube diameter and length and average fluid velocity. Therefore, it is essential to measure the heat transfer performance of nanofluids directly under flow conditions. Researchers have shown that nanofluids have not only better heat conductivity but also greater convective heat transfer capability than that of base fluids. The following section provides the wide usage and effective utilization of nanofluids in heat exchangers as heat transfer fluids. Here are some of the advantages of nanofluids as shown below:

Heat transfer plays an important role in the enhancement of thermal energy storage in phase change material (PCM). The effective utilization of solar thermal energy can be obtained by proper storage of that energy. There are various techniques for the enhancement solar thermal storage in phase change material such as introduction of wire brushes, honey comb structure, fins and packed bed storage. In this study the analysis of heat transfer between PCM and heat transfer fluids (HTF) with Spherical and cylindrical finned encapsulations made of copper are done using computational fluid dynamic (CFD) analysis software GAMBIT and Fluent 6.2. The analysis is done in two modes as charging and discharging. During the charging mode the input is given in terms of temperature to the heat transfer fluid and the amount of heat transfer inside the PCM encapsulation is taken as output. During the discharging process the output temperature in the PCM is given as input and the amount of heat transferred to the heat transfer fluid is noted. The results from CFD analysis conclude that the heat transfer is more in finned encapsulations than that of without finned encapsulations and the copper sphere with fins is considered to be the best out of all other encapsulations.

The higher thermal conductivity of material conducts the heat easier from the hot fluid to the cold fluid. The concept of helical baffle heat exchangers was developed for the first time in Czechoslovakia. The Helical baffle heat exchanger, also known as ‘Helix changer’, is a superior shell and tube exchanger solution that removes many of the inherent deficiencies of conventional segmental baffle exchangers. Helical baffle heat exchangers have shown very effective performance especially for the cases in which the heat transfer coefficient in shell side is controlled; or less pressure drop and less fouling are expected.

Abstract. This paper presents a procedure for experimental determining the local heat transfer coefficient in the rotor-stator cavity. As an operating medium is used a hot air with various mass flow rate and rotating speed of the cavity wall. The surface temperature and heat flux distribution takes into account the change of material properties as a function of thermal distribution.

fluid inlet and exit positions after steady state has been reached. Steady state was determined when the temperatures remained constant with time for a 10 min. period. The mass flow rate (kg/s) of the fluid flowing inside the tube, and heat transfer rate (W) were plotted and the result shown in Fig.2.

Natural Convection Heat Transfer, Heat Sink, Mounting Angle, Stagnation Zone... Heat sink is a passive heat exchanger that transfers heat generated by an electronic or a.[r]