scholarly journals Experimental analysis of heat transfer coefficient in counter flow shell and helical coil tube heat exchanger with hybrid nanofluids to enhance heat transfer rate using in food processing industries

2021 ◽  
Vol 12 (2) ◽  
pp. 2868-2875
Author(s):  
D. Sarath Chandra, Et. al.
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Food Processing ◽  
Transfer Rate ◽  
Base Fluid ◽  
Enhance Heat Transfer ◽  
Counter Flow ◽  
Tube Heat Exchanger

The impact of overall heat transfer coefficient and the pressure drop on performance of a counter flow helical tube heat exchanger with Cu-Ni-water hybrid nanofluid are computed. To evaluate heat transfer rate for a mix of base fluid with copper and nickel nanoparticles of volume concentrations 0.02,0.04 and 0.06 are added. To control the sedimentation of nanoparticles in the base fluid Ultrasonication followed by magnetic stirrer method is used. In this work experiments are conducted with to enhance heat transfer rate rather than stability of nanoparticles. Experiments are conducted for different concentrations and coil turns under laminar flow regime. The results are shown that 0.04 % vol of Cu-Ni/H2O with 12 turns is more predominate foe food processing applications due to its consistency in maintaining a constant temperature.

The Shell and Tube Heat Exchanger Efficiency and Its Relation to Effectiveness

2003 ◽  
Author(s):  
Ahmad Fakheri
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Counter Flow ◽  
Tube Heat Exchanger ◽  
Optimum Heat ◽  
Flow Heat ◽  
Shell And Tube

The heat exchanger efficiency is defined as the ratio of the actual heat transfer in a heat exchanger to the optimum heat transfer rate. The optimum heat transfer rate, qopt, is given by the product of UA and the Arithmetic Mean Temperature Difference, which is the difference between the average temperatures of hot and cold fluids. The actual rate of heat transfer in a heat exchanger is always less than this optimum value, which takes place in a balanced counter flow heat exchanger. It is shown that for parallel flow, counter flow, and shell and tube heat exchanger the efficiency is only a function of a single nondimensional parameter called Fin Analogy Number. Remarkably, the functional dependence of the efficiency of these heat exchangers on this parameter is identical to that of a constant area fin with an insulated tip. Also a general algebraic expression as well as a generalized chart is presented for the determination of the efficiency of shell and tube heat exchangers with any number of shells and even number of tube passes per shell, when the Number of Transfer Units (NTU) and the capacity ratio are known. Although this general expression is a function of the number of shells and another nondimensional group, it turns out to be almost independent of the number of shells over a wide range of practical interest. The same general expression is also applicable to parallel and counter flow heat exchangers.

Prediction of Non-Uniform Frost Distribution on a Fin Tube Heat Exchanger

2013 ◽  
Author(s):  
Jieun Hwang ◽  
Keumnam Cho
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Heat Pump ◽  
Transfer Rate ◽  
Volume Flow Rate ◽  
Local Data ◽  
Tube Heat Exchanger ◽  
Side Pressure ◽  
Fin Tube

Heat exchanger experiences frost on its surface when it operates below 0°C under heating condition of the heat pump. Since frost blocks air flow through the fin tube heat exchanger, it increases air-side pressure drop and deteriorates heat transfer rate of the heat exchanger. Prediction of the frost profiles on the heat exchanger is needed to minimize the unfavorable effect on the heat exchanger by frost. The present study predicts non-uniform frost distribution on the surface of fin-tube heat exchanger and shows its accuracy by comparing with measured profiles. Fin and tube heat exchanger for heat pump was considered for the frost prediction under practical refrigerant and air conditions. Non-uniform frost pattern was predicted by using segment by segment method of the heat exchanger. Heat transfer rate and exit temperature of air and refrigerant for each segment were calculated by applying ε-NTU method. Air volume flow rate in the front of the heat exchanger was decreased as frost goes on. It was utilized for the prediction of the frost formation. Numerically predicted results were compared with measured local data. They agreed within ±10.4% under the ISO 5151 condition.

Performance Evaluation of Tube-in-Tube Heat Exchanger Using Nanofluids

2015 ◽  
Vol 787 ◽  
pp. 72-76 ◽  
Author(s):  
V. Naveen Prabhu ◽  
M. Suresh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Element Analysis ◽  
Tube Heat Exchanger

Nanofluids are fluids containing nanometer-sized particles of metals, oxides, carbides, nitrides, or nanotubes. They exhibit enhanced thermal performance when used in a heat exchanger as heat transfer fluids. Alumina (Al2O3) is the most commonly used nanoparticle due to its enhanced thermal conductivity. The work presented here, deals with numerical simulations performed in a tube-in-tube heat exchanger to study and compare flow characteristics and thermal performance of a tube-in-tube heat exchanger using water and Al2O3/water nanofluid. A local element-by-element analysis utilizing e-NTU method is employed for simulating the heat exchanger. Profiles of hot and cooling fluid temperatures, pressure drop, heat transfer rate along the length of the heat exchanger are studied. Results show that heat exchanger with nanofluid gives improved heat transfer rate when compared with water. However, the pressure drop is more, which puts a limit on the operating conditions.

Numerical Study of Shellside Performance of Heat Transfer and Flow Resistance for Heat Exchanger with Trefoil-Hole Baffles

2012 ◽  
Vol 557-559 ◽  
pp. 2141-2146
Author(s):  
Yong Hua You ◽  
Ai Wu Fan ◽  
Chen Chen ◽  
Shun Li Fang ◽  
Shi Ping Jin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Numerical Study ◽  
Shell Side ◽  
Tube Heat Exchanger

Trefoil-hole baffles have good thermo-hydraulic performances as the support of heat pipes, however the published research paper is relatively limited. The present paper investigates the shellside thermo-hydraulic characteristics of shell-and-tube heat exchanger with trefoil-hole baffles (THB-STHX) under turbulent flow region, and the variations of shellside Nusselt number, pressure loss and overall thermo-hydraulic performance (PEC) with Reynolds number are obtained for baffles of varied pitch with the numerical method. CFD results demonstrate that the trefoil-hole baffle could enhance the heat transfer rate of shell side effectively, and the maximal average Nusselt number is augmented by ～2.3 times that of no baffle, while average pressure loss increases by ～9.6 times. The PEC value of shell side lies in the range of 16.3 and 73.8 kPa-1, and drops with the increment of Reynolds number and the decrement of baffle pitch, which indicates that the heat exchanger with trefoil-hole baffles of larger pitch could generate better overall performance at low Reynolds number. Moreover, the contours of velocity, turbulent intensity and temperature are presented for discussions. It is found that shellside high-speed jet, intensive recirculation flow and high turbulence level could enhance the heat transfer rate effectively. Besides good performance, THB-STHXs are easily manufactured, thus promise widely applied in various industries.

scholarly journals Enhancing Heat Transfer in Tube Heat Exchanger by Inserting Discrete Twisting Tapes with Different Positions

2019 ◽  
Vol 25 (8) ◽  
pp. 39-51
Author(s):  
Nassr Fadhil Hussein ◽  
Abdulrahman Shakir Mahmood
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Constant Heat Flux ◽  
Vertical Position ◽  
Maximum Heat ◽  
Tube Heat Exchanger ◽  
Twisted Tapes ◽  
Maximum Heat Transfer

Enhancement of heat transfer in the tube heat exchanger is studied experimentally by using discrete twisted tapes. Three different positions were selected for inserting turbulators along tube section (horizontal position by α= 00, inclined position by α= 45 0 and vertical position by α= 900). The space between turbulators was fixed by distributing 5 pieces of these turbulators with pitch ratio    PR = (0.44). Also, the factor of constant heat flux was applied as a boundary condition around the tube test section for all experiments of this investigation, while the flow rates were selected as a variable factor (Reynolds number values vary from 5000 to 15000). The results show that using discrete twisted tapes enhances the heat transfer rate by about 60.7-103.7 % compared with plane tube case. Also, inserting turbulators with inclined position offers maximum heat transfer rate by 103.7%.  

Arithmetic Mean Temperature Difference and the Concept of Heat Exchanger Efficiency

2003 ◽  
Author(s):  
Ahmad Fakheri
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Arithmetic Mean ◽  
Counter Flow ◽  
Mean Temperature ◽  
Optimum Heat

In this paper, it is shown that the Arithmetic Mean Temperature Difference, which is the difference between the average temperatures of hot and cold fluids, can be used instead of the Log Mean Temperature Difference (LMTD) in heat exchanger analysis. For a given value of AMTD, there exists an optimum heat transfer rate, Qopt, given by the product of UA and AMTD such that the rate of heat transfer in the heat exchanger is always less than this optimum value. The optimum heat transfer rate takes place in a balanced counter flow heat exchanger and by using this optimum rate of heat transfer, the concept of heat exchanger efficiency is introduced as the ratio of the actual to optimum heat transfer rate. A general algebraic expression as well as a chart is presented for the determination of the efficiency and therefore the rate of heat transfer for parallel flow, counter flow, single stream, as well as shell and tube heat exchangers with any number of shells and even number of tube passes per shell. In addition to being more intuitive, the use of AMTD and the heat exchanger efficiency allow the direct comparison of the different types of heat exchangers.

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