Development of two-dimensional code for heat exchanger thermal performance prediction – Effects of airflow velocity distribution (original) (raw)
FEDSM2013-16148 AEROTHERMAL MANAGEMENT OF VEHICLE HEAT EXCHANGERS – PARAMETRIC ANALYSIS
This paper presents a numerical analysis focused on the relation between non-uniformities in flow velocity and temperature distributions upstream of heat exchangers and their thermal performance. For this purpose, a two-dimensional computation code is developed to compute thermal performance, knowing the air flow velocity distribution upstream of an air-liquid heat exchanger, the heat exchanger liquid flow rate and the air and liquid inlet temperatures. A parametric analysis is then presented of the relation between the thermal performance of the heat exchanger and the different parameters above. It is found that non-uniformities in air velocity and water flow distributions can decrease the thermal performance of a heat exchanger from 33 to 42%. However, non-uniformity in the air temperature distribution can increase thermal performance by up to 5%. INTRODUCTION Heat exchangers are used in a wide variety of applications, among them military and aerospace, power plants, nuclear react...
This investigation deals with the performance prediction of the cross flow air cooled heat exchangers. Experimental and theoretical studies were conducted to perform the optimization of the thermal design of the heat exchanger. The experimental work was carried out by two different types and sizes of finned tube air cooled heat exchangers. An experimental rig was built for this object which provides hot water at the range of (40 to 70) Cº with water circulating rate of (200 to 1800) l/hr at absolute pressure of (2) bar. A centrifugal fan was installed as a major part of the experimental rig to provide atmospheric air with volumetric flow rate of (1250 and 2500) cfm. The performance parameters measured in the experimental work were flow rates and temperature at the entering and leaving sides of the process and service fluids passing through the heat exchanger. Further, the water side operating pressure at the inlet and exit ports, and the wet bulb temperature of air on both sides of ...
A-Type Heat Exchanger Simulation Using 2-D CFD for Airside Heat Transfer and Pressure Drop
2008
A-Type heat exchangers are used to meet required heat load with minimum duct dimensions in air-conditioning applications. This greatly reduces the air-conditioning system footprint in residential and commercial applications. The angle and tube spacing of the A-type heat exchangers should be optimized for minimum duct size and maximum heat load. However, existing air side heat transfer and pressure drop correlations may not be applicable for A-type heat exchangers due to non-uniform air velocity profile and temperature distribution in the heat exchanger. In this paper, a new technique is proposed where a segment-by-segment NTU based coil model is coupled with automated 2-D CFD simulations of air flow through the heat exchanger. The 2-D CFD simulations are used to calculate the heat transfer coefficient on each tube as well as the inlet air velocity profile on the coil face. The segmented NTU solver calculates NTU based on the CFD calculated heat transfer coefficient on the airside, the refrigerant side heat transfer (from available correlations), and tube-fin arrangement. In the current investigations, a parametric study was performed by varying the tube pitch, row pitch and the coil angle. The proposed framework is used to automatically generate the mesh and run the 2-D double precision CFD simulations using commercial CFD tools for the different configurations. The NTU calculations are performed using a validated segment by segment fin and tube heat exchanger model developed by the authors. The simulation results for each coil configuration were compared against the base line heat exchanger configurations. The trade-off between the heat exchanger enclosure volume and material cost is presented.
Heat Exchangers Modeling using Industrial Wind Tunnel Simulation for Automobile Industry
International Journal of Innovative Technology and Exploring Engineering, 2020
In the industry 4.0 eras, it is necessary to analyze each parameter precisely. In case of heat transfer studies, the automobile and aerodynamic industry is gaining more and more attention. Many heat exchangers are designed and tested in industry but for any specific product thermal characteristics can be different which depends on the scenario of use of that product. Heat exchangers can test with fluid, air etc. For internal machines like bearing cooling fluid can be used but in case of automobile, aerodynamics air flow is important element. This paper presents the simulation and analytical modeling of various heat exchangers. This can be very useful for lowering the insulation damages or foil damages of vehicle. The wind tunnel test is carried with constant wind flow to assure that vehicle speed and cooling can be moderate without issue of cooling.
AIAA AVIATION 2021 FORUM, 2021
A surface air-cooled oil cooler (SACOC) is a passive heat exchanger used to evacuate a large quantity of heat from the oil circuit of a turbofan engine to its secondary flow with minimal perturbation. Using the secondary flow as a heat sink has the advantage of the evacuated enthalpy being available in the nozzle. The performance of a SACOC is therefore measured in terms of maximum heat release capacity with minimal pressure loss and flow perturbations. These heat exchangers are typically composed of parallel fins and are usually tested in bespoke wind tunnels where the interaction between the three-dimensional high velocity flow and the heat exchangers is evaluated. Modern numerical computations that include the solution of the fluid equations in the flow field and a conjugate thermal problem can be also performed. This numerical approach, once validated, allows a complete and computationally affordable analysis of the aero-thermodynamic performance of the SACOC. In this work, a first comparison between both experimental and computational perspectives is presented in terms of pressure and temperature profiles to achieve a complete characterization of the device. This double experimental numerical perspective allows comparing the behaviour of the different fins of the SACOC depending on their relative position but also to trust the numerical conclusions with experimental robust data.
IRJET, 2020
The cross-flow heat exchangers are employed in variety of commercial, domestic and industrial applications such as air conditioning, power generation, refrigeration, petrochemical, petroleum, and other industries because of the wide range of design possibilities, simple manufacturing technology, low maintenance and low cost. The performance of the heat exchanger is a significant effect on the performance of cooling systems. The determination of ε-NTU relation by mathematical model for cross-flow heat exchangers with complex flow arrangements is presented in the current work. Tube element approach is used in this model. In this approach, the coil along the path of the tube fluid is discretized, to find the outlet temperatures of the heat exchanger. Tube side fluid temperature is supposed to be constant in each cross section of the element since the heat capacity ratio C*=Cmin / Cmax in the element tends toward zero. Therefore temperature is regulated by the effectiveness of a local element corresponding to a condenser or evaporator type element. A mathematical model, Numerical discretization, and algorithm for calculating the effectiveness of a cross-flow heat exchanger are described in this paper. The proposed model represents valuable research tool for efficiency of the heat exchangers in experimental studies and theoretical work.
Prediction of Thermal Performance of Multi Pass Cross Flow Heat Exchangers
A steady state heat exchanger performance model termed the matrix approach was previously developed by Silaipillayarputhur and Idem to study the performance of multi-row multi-pass cross flow tubular heat exchangers. This paper utilizes the matrix approach to study the steady state sensible performance of cross flow heat exchangers subjected to varying thermal and design conditions. Parallel and counter cross flow heat exchangers have been considered in this study. The cross flow heat exchanger's input and the thermal performance are described through dimensionless parameters. Since the heat exchanger's performance is observed at each individual tube pass and since the performance is evaluated through meaningful and industry recognized dimensionless input parameters, this study shall benefit the heat exchanger designers in designing an optimum and a cost efficient heat exchanger. The "intermediate" thermal performance of cross flow heat exchangers has not yet been described in the available literature.
Computational Fluid Dynamics and Heat Transfer Analysis for a Novel Heat Exchanger
Journal of Heat Transfer, 2015
Computational fluid dynamics (CFD) and heat transfer simulations are conducted for a novel heat exchanger. The heat exchanger consists of semi-circle cross-sectioned tubes that create narrow slots oriented in the streamwise direction. Numerical simulations are conducted for Reynolds numbers (Re) ranging from 700 to 30,000. Three-dimensional turbulent flows and heat transfer characteristics in the tube bank region are modeled by the k-e Reynolds-averaged Navier-Stokes (RANS) method. The flow structure predicted by the two-dimensional and three-dimensional simulations is compared against that observed by the particle image velocimetry (PIV) for Re of 1500 and 4000. The adequate agreement between the predicted and observed flow characteristics validates the numerical method and the turbulent model employed here. The three-dimensional and the twodimensional steady flow simulations are compared to determine the effects of the wall on the flow structure. The wall influences the spatial structure of the vortices formed in the wake of the tubes and near the exit of the slots. The heat transfer coefficient of the slotted tubes improved by more than 40% compare to the traditional nonslotted tubes.
Design Heat Exchanger: Optimization and Efficiency
International Journal of Advanced Network, Monitoring and Controls, 2020
Modern commercial and residential buildings procure HVAC systems, to provide heating and cooling for designed open and enclosed spaces to dissipate throughout the accustomed zones. HVAC (heating, ventilating, and air conditioning) systems have become a required industry standard for the construction of new buildings. The objective is the optimization of a heat exchanger model by resolving common system concerns; efficiency, fouling, leakage, dead zones, and vibration. These issues are prevalent in the HVAC industry, which are critical to the under-performing heat exchangers. The heat exchanger was tested at only three different wind speeds (20, 40%, 60%) to take the temperature readings every 5 minutes to allow for maximal heat transfer. The efficiency of heat exchanger at the specified speeds was determined to be .7413 at 20%, .6463 at 40% and .6351 at 60%. Keywords-Heat Exchanger; Efficiency; Buildings;