Presentation on theme: "CFD ANALYSIS OF CROSS FLOW AIR TO AIR TUBE TYPE HEAT EXCHANGER"— Presentation transcript:
1CFD ANALYSIS OF CROSS FLOW AIR TO AIR TUBE TYPE HEAT EXCHANGER Vikas Kumar1*, D. Gangacharyulu2*,Parlapalli MS Rao3 and R. S. Barve41 Centre for Development of Advanced Computing, Pune University Campus, Pune, India2 Thapar Institute of Engineering & Technology, Patiala, India3 Nanyang Technological University, Singapore4 Crompton Greaves Ltd, Kanjur Marg, Mumbai, India
2IntroductionClosed Air Circuit Air Cooled (CACA) electrical motors are used in various industries for higher rating (500 kW and above) applicationsHeat generation due to the energy losses in the windings of motors at various electrical loads under operating conditionCold air is circulated in the motor to remove the heat generatedThe hot air generated in the motor is cooled by using an air to air tube type cross flow heat exchangersThe motor designers are interested to know the temperature distribution of air in the heat exchanger and pressure drop across the tube bundle at various operating parameters, e.g., different hot & cold air temperatures and fluid (hot & cold) flow rates
3Large Electrical Motor Heat exchangerSource: M/S Crompton Greaves Ltd. Mumbai, India
4Heat Exchanger Geometry External hot aircooled airInternal hot airExternal cold aircooled air
5OBJECTIVE Predictions of Pressure Air flow and Predictions ofPressureAir flow andTemperature distributionsin the heat exchangers
7Table 1: Geometrical details of the heat exchanger Sl. No.DescriptionUnitValue/Type1.Overall dimensionmm 1760 x 100 x 7652.Tube inner diameter223.Tube outer diameter264.Tube length16105.No. of tubes-276.Transverse pitch617.Longitudinal pitch41
8Modeling Considerations Geometry has symmetry in width wise.A section of heat exchanger consisting of 9 rows & 3 columns has been considered for analysis. Each column has 9 tubes.Tube is modeled as solid blockage, whereas, the inner volume of the tube has been modeled as blockage with gaseous properties to allow the ambient air to pass through it by using PHOENICS CFD Software.Conduction takes place from the tube wall & convection takes place from the surface of the tube.The partition plate and baffle participate in heat transfer.Temperature & flow distributions have been considered to be three dimensional in nature.k-ε turbulence model has been considered.Hybrid difference scheme has been used.
9Grid generation for heat exchanger The distribution of cells in the three directions are given below:X Direction : 55Y Direction : 48Z Direction : 232The total number of cells in the computational domain is 612,480.
11Table 2: Operating boundary conditions of the heat exchanger Sl. No.Input parametersUnitValue1.Temperature of cold airoC352.Temperature of hot air633.Volumetric flow rate of cold aircfm (cu.m/m)388 (10.98)4.Volumetric flow rate of hot air228.80(6.48)
12Results & DiscussionsThe highest pressure region has been observed nearby the top of the separating plate, which may be due to the large change in the momentum of the cold fluid caused by the plate.Hot fluid recirculation has been observed at the top corner of 1st & 4th section.The temperature drop of the hot air in the 1st section of the heat exchanger is higher than 4th section because of the high temperature difference between the cold air and the hot air.
13Fig. 4: Pressure distribution in the heat exchanger
14Fig. 5: Velocity distribution in the heat exchanger
15Fig. 6: Temperature distribution in the heat exchanger
16Fig. 7: Temperature distribution in the tube bundle of the heat exchanger
17Table 3: Comparison of air temperature prediction at various outlets Sl. No.Inlet temperature, oCOutlet temperature, oCRemarksCold airHot air 2nd sectionHot air 3rd sectionHot air1st section4th section1.34.46341.951.846.8Experimental2.44.7049.5543.68PHOENICS Simulation3.616550.944.32
18Fig. 8: A comparison between the results of CFD simulation & experiments
19Fig. 9: Temperature distribution in the heat exchanger – a case study
20Fig. 10: Temperature distribution of the heat exchanger (after modification of central partition plate)
21(Sun Ultra SPARC-450, 300 MHz)Fig. 11: Effect of number of processors in computing time using parallel PHOENICS
22ConclusionsA method for predicting the pressure, velocity & temperature distributions in the tube type heat exchanger associated with CACA large motor has been developed using PHOENICS CFD software.The simulated results predict the temperature distribution reasonably at different locations of the heat exchanger.The CFD model may be used to optimize its thermal performance by varying the location of the baffles & the partition plate in the heat exchanger and in turn to improve the performance of electrical motors.The parallel PHOENICS can be used to reduce the design cycle of the equipment due to fast computation.
23AcknowledgementsM/S Thapar Centre for Industrial Research & Development, Patiala, India for providing the necessary facilities to carry out this projectM/S Crompton Greaves, Mumbai, India for providing the funds in addition to drawing, design data and experimental resultsM/S CHAM, U.K (support team) for technical helpM/S Centre for Development of Advanced Computing (C-DAC), Pune, India for providing the facility to use PARAM for running parallel PHOENICS and funding for presenting this paper