Analysis of a Load-Side Heat Exchanger for a Solar Domestic Hot Water Heating System

1998 ◽  
Vol 120 (4) ◽  
pp. 270-274 ◽  
Author(s):  
T. R. Smith ◽  
P. J. Burns ◽  
D. C. Hittle
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchanger ◽  
Heating System ◽  
Hot Water ◽  
Transfer Coefficients ◽  
Adequate Model ◽  
Domestic Hot Water ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Testing is done of an unpressurized drainback system with a load-side heat exchanger. Analytical calculations for the heat exchanger effectiveness and three models for convective heat transfer coefficients from correlations are compared against the experimental data. TRNSYS simulations were performed using the average effectiveness of 0.78 (the calculated effectiveness varies from 0.68 to 0.95); the results compare favorably with experimental results, indicating that a constant effectiveness is an adequate model for the system.

scholarly journals Experimental Study of Forced Convective Heat Transfer in a Coiled Flow Inverter Using TiO2–Water Nanofluids

2020 ◽  
Vol 10 (15) ◽  
pp. 5225
Author(s):  
Barbara Arevalo-Torres ◽  
Jose L. Lopez-Salinas ◽  
Alejandro J. García-Cuéllar
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Convective Thermal ◽  
Convective Heat Transfer Coefficients

The curved geometry of a coiled flow inverter (CFI) promotes chaotic mixing through a combination of coils and bends. Besides the heat exchanger geometry, the heat transfer can be enhanced by improving the thermophysical properties of the working fluid. In this work, aqueous solutions of dispersed TiO2 nanometer-sized particles (i.e., nanofluids) were prepared and characterized, and their effects on heat transfer were experimentally investigated in a CFI heat exchanger inserted in a forced convective thermal loop. The physical and transport properties of the nanofluids were measured within the temperature and volume concentration domains. The convective heat transfer coefficients were obtained at Reynolds numbers (NRe) and TiO2 nanoparticle volume concentrations ranging from 1400 to 9500 and 0–1.5 v/v%, respectively. The Nusselt number (NNu) in the CFI containing 1.0 v/v% nanofluid was 41–52% higher than in the CFI containing pure base fluid (i.e., water), while the 1.5 v/v% nanofluid increased the NNu by 4–8% compared to water. Two new correlations to predict the NNu of TiO2–water nanofluids in the CFI at Reynolds numbers of 1400 ≤ NRe ≤ 9500 and nanoparticle volume concentrations ranges of 0.2–1.0 v/v% and 0.2–1.5 v/v% are proposed.

Simulation of Heat Transfer to Turbulent Nanofluid Flow in an Annular Passage

2014 ◽  
Vol 925 ◽  
pp. 625-629 ◽  
Author(s):  
C.S. Oon ◽  
A. Badarudin ◽  
S.N. Kazi ◽  
M. Fadhli
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Titanium Oxide ◽  
Convective Heat Transfer Coefficient ◽  
Hot Water ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients

The heat transfer in annular heat exchanger with titanium oxide of 1.0 volume % concentration as the medium of heat exchanger is considered in this study. The heat transfer simulation of the flow is performed by using Computational Fluid Dynamics package, Ansys Fluent. The heat transfer coefficients of water to titanium oxide nanofluid flowing in a horizontal counter-flow heat exchanger under turbulent flow conditions are investigated. The results show that the convective heat transfer coefficient of the nanofluid is slightly higher than that of the base fluid by several percents. The heat transfer coefficient increases with the increase of the mass flow rate of hot water and also the nanofluid.

Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Yantao Li ◽  
Yulong Ji ◽  
Katsuya Fukuda ◽  
Qiusheng Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convection Heat Transfer ◽  
Bulk Liquid ◽  
Transfer Coefficients ◽  
Forced Convective Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Abstract This paper presents an experimental investigation of the forced convective heat transfer of FC-72 in vertical tubes at various velocities, inlet temperatures, and tube sizes. Exponentially escalating heat inputs were supplied to the small tubes with inner diameters of 1, 1.8, and 2.8 mm and effective heated lengths between 30.1 and 50.2 mm. The exponential periods of heat input range from 6.4 to 15.5 s. The experimental data suggest that the convective heat transfer coefficients increase with an increase in flow velocity and µ/µw (refers to the viscosity evaluated at the bulk liquid temperature over the liquid viscosity estimated at the tube inner surface temperature). When tube diameter and the ratio of effective heated length to inner diameter decrease, the convective heat transfer coefficients increase as well. The experimental data were nondimensionalized to explore the effect of Reynolds number (Re) on forced convection heat transfer coefficient. It was found that the Nusselt numbers (Nu) are influenced by the Re for d = 2.8 mm in the same pattern as the conventional correlations. However, the dependences of Nu on Re for d = 1 and 1.8 mm show different trends. It means that the conventional heat transfer correlations are inadequate to predict the forced convective heat transfer in minichannels. The experimental data for tubes with diameters of 1, 1.8, and 2.8 mm were well correlated separately. And, the data agree with the proposed correlations within ±15%.

Size Effect on Thermal Characteristic of Tubular Heat Exchanger at Miniscale and Microscale

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Ankush D. Tharkar ◽  
Shripad P. Mahulikar
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Performance Parameter ◽  
Annular Space ◽  
Transfer Coefficients ◽  
Tubular Heat Exchanger ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Abstract The scope for the heat transfer enhancement in the tubular heat exchanger is high due to its unique property of having two separate convective heat transfer coefficients. The variation of diameter and annular space has a direct effect on the value of convective heat transfer coefficients due to their inverse relation. Thus, the strong emphasis must be given on the influence of diameter and annular space on the thermal characteristics of the tubular heat exchanger. In this numerical analysis, peculiarities in the improvement of the performance parameters are studied with the variation in the value of inlet velocities of the fluids (cold and hot), inner pipe diameter, and annular space for the combination of dimensional range such as miniscale and microscale range. The inner tube diameter is observed to be sensitive to the improvement in the performance parameter. The growth in the performance parameter of the tubular micro heat exchanger is found to be higher when both the values of diameter and annular space are in the microscale range.

The Correlation of Heat Transfer Coefficients for the Laminar Natural Convection in a Circular Finned-Tube Heat Exchanger

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Hie Chan Kang ◽  
Se-Myong Chang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Finned Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Laminar Natural Convection

This study proposes an empirical correlation for laminar natural convection applicable to external circular finned-tube heat exchangers with wide range of configuration parameters. The transient temperature response of the heat exchangers was used to obtain the heat transfer coefficient, and the experimental data with their characteristic lengths are discussed. The data lie in the range from 1 to 1000 for Rayleigh numbers based on the fin spacing: the ratio of fin height to tube diameter ranges from 0.1 to 0.9, and the ratio of fin pitch to height ranges from 0.13 to 2.6. Sixteen sets of finned-tube electroplated with nickel–chrome were tested. The convective heat transfer coefficients on the heat exchangers were measured by elimination of the thermal radiation effect from the heat exchanger surfaces. The Nusselt number was correlated with a newly suggested composite curve formula, which converges to the quarter power of the Rayleigh number for a single cylinder case. The proposed characteristic length for the Rayleigh number is the fin pitch while that for the Nusselt number is mean flow length, defined as half the perimeter of the mean radial position inside the flow region bounded by the tube surface and two adjacent fins. The flow is regarded as laminar, which covers heat exchangers from a single horizontal cylinder to infinite parallel disks. Consequently, the result of curve fitting for the experimental data shows the reasonable physical interpretation as well as the good quantitative agreement with the correction factors.

scholarly journals Numerical Investigation On The Impingement Of A Circular Jet Of Nanofluids On A Circular Flat Plate

2021 ◽  
Author(s):  
Dhimitri Kucuqi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Convective Heat Transfer ◽  
Experimental Model ◽  
Convective Heat ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Maximum Heat ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

A numerical study was conducted to investigate and validate experimental convective heat transfer coefficient data associated with an Al2O3-H2O nanofluid through the use of an impingement jet on a flat, circular disk. It was observed that, in conjunction with experimental data, nanofluids provided increased local convective heat transfer coefficients in comparison to the base fluid. Nanofluid concentrations outlined in the experimental model, from 0.0198 to 0.0757 wt%, were investigated in a numerical model and resulting convective heat transfer coefficients were compared. In contrast to the experimental model, the maximum heat transfer enhancement occurred at the nanofluid concentration of 0.0757 wt%. In addition, several other models were tested with various Reynolds numbers and jet height-to-jet diameter ratios for further investigation along with discussion of sources of error. Overall, in comparison to experimental data, the lowest percentage errors achieved for the Reynolds numbers of 4245.7 and 8282 were 17.9% and 34.9%, respectively.

Cooling of a Finned Cylinder by a Jet Flow of Air

2005 ◽  
Vol 127 (12) ◽  
pp. 1416-1421 ◽  
Author(s):  
F. Gori ◽  
M. Borgia ◽  
A. Doro Altan ◽  
M. Mascia ◽  
I. Petracci
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Jet Flow ◽  
Steel Tube ◽  
Finned Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Smooth Cylinder ◽  
Convective Heat Transfer Coefficients

A submerged slot jet of air is used to cool an externally finned cylinder, heated by electric current. The cylinder ensemble is made of a stainless steel finned tube and a Teflon bar core inside. Five thermocouples, pressed inside the steel tube by the Teflon bar, measure the wall temperature to determine local and mean convective heat transfer coefficients. The local Nusselt number has the maximum on the impinging point and the minimum on the rear point. The variation of local and mean Nusselt numbers with the distance from the slot exit is investigated. Empirical expressions are proposed to correlate the experimental data. The cooling of a finned cylinder with a jet flow realizes a higher heat transfer as compared to a smooth cylinder.

scholarly journals Numerical Investigation On The Impingement Of A Circular Jet Of Nanofluids On A Circular Flat Plate

2021 ◽  
Author(s):  
Dhimitri Kucuqi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Convective Heat Transfer ◽  
Experimental Model ◽  
Convective Heat ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Maximum Heat ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

A numerical study was conducted to investigate and validate experimental convective heat transfer coefficient data associated with an Al2O3-H2O nanofluid through the use of an impingement jet on a flat, circular disk. It was observed that, in conjunction with experimental data, nanofluids provided increased local convective heat transfer coefficients in comparison to the base fluid. Nanofluid concentrations outlined in the experimental model, from 0.0198 to 0.0757 wt%, were investigated in a numerical model and resulting convective heat transfer coefficients were compared. In contrast to the experimental model, the maximum heat transfer enhancement occurred at the nanofluid concentration of 0.0757 wt%. In addition, several other models were tested with various Reynolds numbers and jet height-to-jet diameter ratios for further investigation along with discussion of sources of error. Overall, in comparison to experimental data, the lowest percentage errors achieved for the Reynolds numbers of 4245.7 and 8282 were 17.9% and 34.9%, respectively.

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