scholarly journals Using CFD To Assess The Impact of Helical Baffle On The First- Law And Second-Law Performance of Water-CuO Nanofluid Inside A Hairpin Heat Exchanger

2021 ◽  
Author(s):  
Amin Shahsavar ◽  
Davood Toghraie ◽  
Pouya Barnoon
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Performance Metrics ◽  
Volume Concentration ◽  
Second Law ◽  
Convection Flow ◽  
Numerical Assessment ◽  
Helical Baffle ◽  
Forced Convection Flow ◽  
The Impact

Abstract This study is devoted to the numerical assessment of the influence of helical baffle on the hydrothermal aspects and irreversibility behavior of the turbulent forced convection flow of water-CuO nanofluid (NF) inside a hairpin heat exchanger. The variations of the first-law and second-law performance metrics are investigated in terms of Reynolds number (Re), volume concentration of NF (φ) and baffle pitch (B). The results showed that the NF Nusselt number grows the rise of both the Re and φ whereas it declines by boosting with the rise of baffle pitch. In addition, the outcomes depicted that the rise of both the T and φ results in the rise of pressure drop, while it declines with the increase of baffle pitch. Moreover, it was found that the best first-law performance of the NF belongs to the case B=33.3 mm, φ=2% and Renf=10000. Furthermore, it was shown that irreversibilities due to fluid friction and heat transfer augment with the rise of Re while the rise of baffle pitch results in the decrease of frictional irreversibilities. Finally, the outcomes revealed that with the rise of baffle pitch, the heat transfer irreversibilities first intensifies and then diminishes.

Heat Transfer Performance of Different Nanofluids Flows in a Helically Coiled Heat Exchanger

2013 ◽  
Vol 832 ◽  
pp. 160-165 ◽  
Author(s):  
Mohammad Alam Khairul ◽  
Rahman Saidur ◽  
Altab Hossain ◽  
Mohammad Abdul Alim ◽  
Islam Mohammed Mahbubul
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Transfer Performance

Helically coiled heat exchangers are globally used in various industrial applications for their high heat transfer performance and compact size. Nanofluids can provide excellent thermal performance of this type of heat exchangers. In the present study, the effect of different nanofluids on the heat transfer performance in a helically coiled heat exchanger is examined. Four different types of nanofluids CuO/water, Al2O3/water, SiO2/water, and ZnO/water with volume fractions 1 vol.% to 4 vol.% was used throughout this analysis and volume flow rate was remained constant at 3 LPM. Results show that the heat transfer coefficient is high for higher particle volume concentration of CuO/water, Al2O3/water and ZnO/water nanofluids, while the values of the friction factor and pressure drop significantly increase with the increase of nanoparticle volume concentration. On the contrary, low heat transfer coefficient was found in higher concentration of SiO2/water nanofluids. The highest enhancement of heat transfer coefficient and lowest friction factor occurred for CuO/water nanofluids among the four nanofluids. However, highest friction factor and lowest heat transfer coefficient were found for SiO2/water nanofluids. The results reveal that, CuO/water nanofluids indicate significant heat transfer performance for helically coiled heat exchanger systems though this nanofluids exhibits higher pressure drop.

Numerical Investigation on Heat Transfer of Al2O3/Water Nanofluid in a Shell and Tube Heat Exchanger

2014 ◽  
Vol 591 ◽  
pp. 3-6
Author(s):  
M. Raja ◽  
R. Vijayan ◽  
R. Vivekananthan ◽  
M.A. Vadivelu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Numerical Investigation ◽  
Volume Concentration ◽  
Heat Transfer Characteristics ◽  
Tube Heat Exchanger ◽  
Transfer Characteristics ◽  
Shell And Tube ◽  
Suspended Nanoparticles

In the present work, the effect of nanofluid in a shell and tube heat exchanger was studied numerically. The effects of Reynolds number, volume concentration of suspended nanoparticles on the heat transfer characteristics were investigated using CFD software. Finally, the effect of the nanofluid on Shell and tube heat exchanger performance was studied and compared to that of a conventional fluid (i.e., water).

A comprehensive survey on utilization of hybrid nanofluid in plate heat exchanger with various number of plates

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Faraz Afshari ◽  
Azim Doğuş Tuncer ◽  
Adnan Sözen ◽  
Halil Ibrahim Variyenli ◽  
Ataollah Khanlari ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Flow Behavior ◽  
Plate Heat Exchanger ◽  
Single Type ◽  
Hybrid Nanofluid ◽  
Content Type ◽  
Plate Heat ◽  
The Impact

Purpose Using suspended nanoparticles in the base fluid is known as one of the most efficient ways for heat transfer augmentation and improving the thermal efficiency of various heat exchangers. Different types of nanofluids are available and used in different applications. The main purpose of this study is to investigate the effects of using hybrid nanofluid and number of plates on the performance of plate heat exchanger. In this study, TiO2/water single nanofluid and TiO2-Al2O3/water hybrid nanofluid with 1% particle weight ratio have been used to prepare hybrid nanofluid to use in plate type heat exchangers with three various number of plates including 8, 12 and 16. Design/methodology/approach The experiments have been conducted with the aim of examining the impact of plates number and used nanofluids on heat transfer enhancement. The performance tests have been done at 40°C, 45°C, 50°C and 55°C set outlet temperatures and in five various Reynolds numbers between 1,600 and 3,800. Also, numerical simulation has been applied to verify the heat and flow behavior inside the heat exchangers. Findings The results indicated that using both nanofluids raised the thermal performance of all tested exchangers which have a various number of plates. While the major outcomes of this study showed that TiO2-Al2O3/water hybrid nanofluid has priority when compared to TiO2/water single type nanofluid. Utilization of TiO2-Al2O3/water nanofluid led to obtaining an average improvement of 7.5%, 9.6% and 12.3% in heat transfer of heat exchangers with 8, 12 and 16 plates, respectively. Originality/value In the present work, experimental and numerical analyzes have been conducted to investigate the influence of using TiO2-Al2O3/water hybrid nanofluid in various plate heat exchangers. The attained findings showed successful utilization of TiO2-Al2O3/water nanofluid. Based on the obtained results increasing the number of plates in the heat exchanger caused to obtain more increment by using both types of nanofluids.

An Exergy-Based Metric for Evaluating Solar Thermal Absorber Technologies for Gas Heating

2011 ◽  
Author(s):  
Maritza Ruiz ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Loss Factor ◽  
Performance Metrics ◽  
Solar Thermal ◽  
Pumping Power ◽  
Central Receiver ◽  
Gas Heating ◽  
Goodness Factor ◽  
Solar Receiver

The energy conversion effectiveness of the central receiver absorber in concentrating solar thermal power systems is dictated primarily by heat losses, material temperature limits, and pumping power losses. To deliver concentrated solar energy to a gas for process heat applications or gas cycle power generation, there are a wide variety of compact heat exchanger finned surfaces that could be used to enhance the convective transfer of absorbed solar energy to the gas stream flowing through the absorber. In such circumstances, a key design objective for the absorber is to maximize the heat transfer thermodynamic performance while minimizing the pumping power necessary to drive the gas flow through the fin matrix. This paper explores the use of different performance metrics to quantify the combined heat transfer, thermodynamic and pressure loss effectiveness of enhanced fins surfaces used in solar thermal absorbers for gas heating. Previously defined heat exchanger performance metrics, such as the “goodness factor”, are considered, and we develop and explore the use of a new metric, the “loss factor”, for determining the preferred enhanced fin matrix surfaces for concentrated solar absorbers. The loss factor, defined as the normalized exergy loss in the receiver, can be used for nondimensional analysis of the desirable qualities in an optimized solar receiver design. In comparison to previous goodness factor methods, the loss factor metric has the advantage that it quantifies the trade-off between trying to maximize the solar exergy transferred to the gas (high heat transfer rate and delivery at high temperature) and minimizing the pumping exergy loss. In this study, the loss factor is used to compare current solar receiver designs, and designs that use a variety of available plate-finned compact heat transfer surfaces with known Colburn factor (j) and friction factor (f) characteristics. These examples demonstrate how the loss factor metric can be used to design and optimize novel solar central receiver systems, and they indicate fin matrix surfaces that are particularly attractive for this type of application.

scholarly journals Second Law Analysis for the Experimental Performances of a Cold Heat Exchanger of a Stirling Refrigeration Machine

Entropy ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 215 ◽  
Author(s):  
Steve Djetel-Gothe ◽  
François Lanzetta ◽  
Sylvie Bégot
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Entropy Generation ◽  
Mass Flow ◽  
Hydraulic Diameter ◽  
Entropy Generation Rate ◽  
Second Law ◽  
Water Mixture ◽  
Fluid Friction ◽  
Refrigeration Machine

The second law of thermodynamics is applied to evaluate the influence of entropy generation on the performances of a cold heat exchanger of an experimental Stirling refrigeration machine by means of three factors: the entropy generation rate N S , the irreversibility distribution ratio ϕ and the Bejan number B e | N S based on a dimensionless entropy ratio that we introduced. These factors are investigated as functions of characteristic dimensions of the heat exchanger (hydraulic diameter and length), coolant mass flow and cold gas temperature. We have demonstrated the role of these factors on the thermal and fluid friction irreversibilities. The conclusions are derived from the behavior of the entropy generation factors concerning the heat transfer and fluid friction characteristics of a double-pipe type heat exchanger crossed by a coolant liquid (55/45 by mass ethylene glycol/water mixture) in the temperature range 240 K < TC < 300 K. The mathematical model of entropy generation includes experimental measurements of pressures, temperatures and coolant mass flow, and the characteristic dimensions of the heat exchanger. A large characteristic length and small hydraulic diameter generate large entropy production, especially at a low mean temperature, because the high value of the coolant liquid viscosity increases the fluid frictions. The model and experiments showed the dominance of heat transfer over viscous friction in the cold heat exchanger and B e | N S → 1 and ϕ → 0 for mass flow rates m ˙ → 0.1 kg.s−1.

Thermal–Hydraulic Performance Analysis of a Convergent Double Pipe Heat Exchanger

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Ahmed T. Al-Sammarraie ◽  
Kambiz Vafai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Contraction Ratio ◽  
Wide Range ◽  
Prandtl Numbers ◽  
Double Pipe ◽  
The Impact ◽  
Pipe Heat

The present investigation proposes an innovative convergent double pipe heat exchanger (C-DPHE). A two-dimensional (2D) axisymmetric heat transfer model with counterflow is employed to analyze the thermal and hydraulic performance of this configuration numerically. The impact of convergence in the flow direction, using a wide range of contraction ratio (Cr), is explored. The effect of Reynolds and Prandtl numbers on the flow and heat transfer is addressed, as well. The model results were validated with available data from the literature, and an excellent agreement has been confirmed. In general, the findings of the present study indicate that increasing the contraction ratio increases heat transfer and pressure drop in the C-DPHE. Moreover, this configuration has a prominent and sustainable performance, compared to a conventional double pipe heat exchanger (DPHE), with an enhancement in heat transfer rate up to 32% and performance factor (PF) higher than one. Another appealing merit for the C-DPHE is that it is quite effective and functional at low Reynolds and high Prandtl numbers, respectively, since no high-operating pumping power is required. Further, the optimal operating conditions can be established utilizing the comprehensive information provided in this work.

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