Showing papers on "Concentric tube heat exchanger published in 2009"

Heat Transfer Coefficients for Turbulent Flow in Concentric Annular Ducts

Abstract: On the basis of a large number of experimental data from the literature, correlations were developed for the heat transfer coefficient for turbulent flow in concentric annular ducts. A proven correlation for heat transfer in circular tubes was extended by factors that take into consideration the effect of the diameter ratio of the annulus and the different boundary conditions for heating or cooling.

Fin Pattern Effects on Air-Side Heat Transfer and Friction Characteristics of Fin-and-Tube Heat Exchangers with Large Number of Large-Diameter Tube Rows

Abstract: Air-side heat transfer and friction characteristics of nine kinds of fin-and-tube heat exchangers, with a large number of tube rows (6, 9, and 12, respectively) and large diameter of tubes (18 mm), are experimentally investigated The test samples consist of three types of fin configurations: plain fin, slit fin, and fin with delta-wing longitudinal vortex generators The working fluid in the tube is steam Results show that when the number of tube is larger than 6, the heat transfer and friction performance for three kinds of fins is independent of the number of tube rows, and slit fin provides higher heat transfer and pressure drop than the other two fins The heat transfer and friction factor correlations for all the heat exchangers were acquired with Reynolds numbers ranging from 4000 to 10000 The air-side performance of heat exchangers with plain fin, slit fin, and longitudinal vortex-generator fin were evaluated under three sets of criteria, and the results showed that the heat exchanger with slit

Effect of Half Length Twisted-Tape Turbulators on Heat Transfer and Pressure Drop Characteristics inside a Double Pipe U-Bend Heat Exchanger

Abstract: Influences of the half length twisted tape insertion on heat transfer and pressure drop characteristics in a U-bend double pipe heat exchanger have been studied experimentally. In the experiments, the swirling flow was introduced by using halflength twisted tape placed inside the inner test tube of the heat exchanger. The results obtained from the heat exchangers with twisted tape insert are compared with those without twisted tape i.e. Plain heat exchanger. The experimental results revealed that the increase in heat transfer rate of the twisted-tape inserts is found to be strongly influenced by tape-induced swirl or vortex motion. The heat transfer coefficient is found to increase by 40% with half-length twisted tape inserts when compared with plain heat exchanger. It was found that on the basis of equal mass flow rate, the heat transfer performance of half-length twisted tape is better than plain heat exchanger, and on the basis of unit pressure drop the heat transfer performance of smooth tube is better than half-length twisted tape. It is also observed that the thermal performance of Plain heat exchanger is better than half length twisted tape by 1.3-1.5 times.

Air-side performance evaluation of three types of heat exchangers in dry, wet and periodic frosting conditions

Abstract: The performances of three types of heat exchangers that use the louver fin geometry: (1) parallel flow parallel fin with extruded flat tubes heat exchanger (PF2), (2) parallel flow serpentine fin with extruded flat tubes heat exchanger (PFSF) and (3) round tube wave plate fin heat exchanger (RTPF) have been experimentally studied under dry, wet and frost conditions and results are presented. The parameters quantified include air-side pressure drop, water retention on the surface of the heat exchanger, capacity and overall heat transfer coefficient for air face velocity 0.9, 2 and 3 m/s, air humidity 70% and 80% and different orientations. The performances of three types of heat exchanger are compared and the results obtained are presented. The condensate drainage behavior of the air-side surface of these three heat exchanger types was studied using both the dip testing method and wind tunnel experiment.

Experimental Study on Pressure Drop and Heat Transfer of Turbulent Flow in Tube in Tube Helical Heat Exchanger

Abstract: In the present study, experiments were conducted for the first time in tube in tube helical heat exchanger at the pilot plant scale to investigate the fluid flow and heat transfer under turbulent f...

Laminated sheet manifold for microchannel heat exchanger

Abstract: A heat exchanger can have a manifold which includes a plurality of laminated sheets that allow a customization of the heat exchanger The design can allow for a more optimal flow of coolant to areas of high load, thereby making the temperature distribution across the heat exchanger more uniform, or intentionally non-uniform Furthermore, the laminated sheets can allow multiple circuits to be employed in the heat exchanger such that different coolants can be utilized therein and maintained separate from one another The tubes can be microchannel tubes A single set of manifolds can be used with multiple heat exchanger cores to provide a more compact heat exchanger Mounting features can be integral with a group of the sheets

Heat exchanger and air conditioner using the same

Abstract: When forming fins and heat transfer tubes by aluminum material, a pressure loss in the tube does not increase and a heat exchanger can be provided having heat transfer performance equal to or higher than a copper tube. The heat exchanger includes fins made of an aluminum material having a low deformation resistance and heat transfer tubes made of an aluminum material having a higher deformation resistance than the aluminum material forming the fins, and on whose internal surface the groove is provided to penetrate the fin to be fixed. It is also arranged that the tube axial direction (a) of the inner surface of the heat transfer tube and the direction (b) of the groove provided on the internal surface of the heat transfer tube are substantially parallel. In this case, the groove direction (b) forms an angle of 0 degrees to 2 degrees with respect to the tube axial direction (a) of the inner surface of the heat transfer tube. The depth of the groove of the heat transfer tube after tube expansion is 0.2 mm to 0.3 mm, and the top width of the ridge top portion is 0.08 mm to 0.18 mm. Further, the number of grooves of the heat transfer tube 20 is 40 to 60, and an apex angle a is 5 degrees to 20 degrees.

Laminar Flow Forced Convection Heat Transfer Behavior of a Phase Change Material Fluid in Finned Tubes

Abstract: The heat transfer behavior of phase change material fluid (PCM) under laminar flow conditions in circular tubes and internally longitudinal finned tubes was studied. An effective specific heat technique was used to model the phase change process. Heat transfer results for a smooth circular tube with PCM fluid were obtained under hydrodynamically and thermally fully developed conditions. Results for the finned tube were obtained using the H2 and T boundary conditions. It was determined that the Nusselt number was strongly dependent on the Stefan number, fin thermal conductivity value, and height of the fins.

Experimental Study and Genetic-Algorithm-Based Correlation on Pressure Drop and Heat Transfer Performances of a Cross-Corrugated Primary Surface Heat Exchanger

Abstract: Heat transfer and pressure drop characteristics of a cross-corrugated (CC) primary surface heat exchanger with different CC passages (P/H=2, θ=60 and 120 deg, called CC2-60 and CC2-120, respectively) in two air sides have been experimentally investigated in this study. It is shown that the corrugation angle (θ) and the ratio of the wavelength P to height H (P/H) are the two key parameters of CC passages to influence the heat transfer and flow friction performances. The heat transfer and friction factor correlations for these two configurations are also obtained with Reynolds numbers ranging from Re =450―5500(CC2-60) and Re =570―6700(CC2-120). At a certain P/H, the Nusselt number, Nu, and the friction factor, f, are affected by the corrugation angle, θ. The heat transfer performance of CC2-120 are much better than that of CC2-60 while the pressure drop of the former is higher than that of the latter, especially at high Reynolds numbers region. The critical Reynolds numbers at which the flow mode transits from laminar to turbulent in the two different passages are also estimated. Furthermore, in this study a genetic algorithm (GA) has been used to determine the coefficients of heat transfer correlations by separation of total heat transfer coefficient without any information of measured wall temperatures. It is concluded that the GA-based separated heat transfer Nusselt number provides a good agreement with the experimental data; the averaged relative deviation by GA (1.95%) is lower than that by regression analysis (2.84%). The inversely yielding wall temperatures agree well with the measured data in turn supporting the reliability of experimental system and measurements. It is recommended that GA techniques can be used to handle more complicated problems and to obtain both-side heat transfer correlations simultaneously, where the conventional Wilson-plot method cannot be applied.