scholarly journals Experimental study on transient behavior of embedded spiral-coil heat exchanger

2015 ◽  
Vol 6 (2) ◽  
pp. 181-190 ◽  
Author(s):  
E. I. Jassim
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Low Cost ◽  
Unit Length ◽  
Transient Behavior ◽  
Efficient Manner ◽  
Spiral Coil ◽  
Coil Performance ◽  
Coil Heat Exchanger ◽  
Coil Heat

Abstract. Spiral coil offers a substantial amount of heat transfer area at a considerably low cost as it does not only have a lower wall resistance but it also achieves a better heat transfer rate in comparison to conventional U-tube arrangement. The general aim of the study is to assess different configurations of spiral coil heat exchangers that can eventually operate in a highly efficient manner. The paper documents the transient behavior of spiral-shaped tubes when the coil is embedded in a rectangular conducting slab. Different arrangements and number of turns per unit length, with fixed volumes, are considered in order to figure out the optimal configuration that maximizes the performance of the heat transfer. The implementation presented in the study is conducted to demonstrate the viability of the use of a large conducting body as supplemental heat storage. The system uses flowing water in the coil and stagnant water in the container. The copper-made coils situated in the center of the slab carries the cold fluid while the container fluid acts as a storage-medium. The water temperature at several depths of the container was measured to ensure uniformity in the temperature distribution of the container medium. Results have shown that the coil orientation, the number of loops, and the Reynolds number, substantially influence the rate of the heat transfer. The vertically-embedded spiral coil has a better performance than the horizontally-embedded spiral coil. Doubling the number of loops is shown to enhance the performance of the coil. Increasing Reynolds Number leads to better coil performance.

A Variable-Curvature Spiral-Coil Heat Exchanger for Automobile Exhaust Heat Recovery

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Yu Zhu ◽  
Fengye Yang ◽  
Yueguang Guo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Recovery ◽  
Heat Transfer Performance ◽  
Cone Angle ◽  
Spiral Coil ◽  
Variable Curvature ◽  
Exhaust Heat ◽  
Coil Heat Exchanger ◽  
Coil Heat

Abstract To improve the fuel efficiency of automobile engines and reduce pollution owing to automobile exhaust, this study discusses a fixed-curvature spiral-coil heat exchanger that recovers exhaust heat. Herein, the heat transfer performance of the spiral coil is studied via experimental testing and numerical simulation. In this study, a new type of variable-curvature spiral coil is designed to improve the efficiency of the heat exchanger. The effect of different conical angles on the resistance and heat transfer performance of the spiral coil within a range of Reynolds numbers of 4000–14,000 was analyzed. The heat exchange efficiency is a combination of the convective heat transfer and the overall heat recovery. The results of this study indicate that for a spiral-coil tube of length L, increasing the cone angle improves the convective heat transfer outside the tube. However, as the flow resistance increases, the exhaust heat recovery of a variable-curvature spiral-coil heat exchanger (VSE) is up to 18.8% higher than that of a constant curvature spiral-coil heat exchanger. The combined performance of VSE is excellent when the cone angle is 15 deg.

Oscillating Heat Transfer Correlations for Spiral-Coil Thermoacoustic Heat Exchangers

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Kriengkrai Assawamartbunlue ◽  
Channarong Wantha
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Transfer Coefficients ◽  
Spiral Coil ◽  
Heat Transfer Coefficients ◽  
Flow Heat ◽  
Heat Transfer Correlations ◽  
Coil Heat Exchanger ◽  
Coil Heat

Heat exchangers are the important parts in thermoacoustic refrigerators. Types and configurations of the heat exchangers affect flow behaviors through stacks, and heat transfer behaviors between working fluids and the heat exchangers. Steady-flow heat transfer correlations to design a heat exchanger are not suitable for the thermoacoustic refrigerators due to their oscillatory flow conditions in resonator tubes. In this paper, a heat transfer correlation for a spiral-coil heat exchanger is presented. The results from the experimental study were used to develop an empirical equation between the Colburn-j factor, the Prandtl number, and the Reynolds number to correlate the oscillating heat transfer coefficient at the spiral-coil heat exchangers. The results showed that using steady-flow heat transfer correlations for analyses and design of the heat exchanger could result in distinguished errors. The heat transfer correlations developed for oscillatory flows on fin heat exchangers are also not suitable to predict heat transfer coefficients for spiral-coil heat exchanger due to difference in flow behaviors on the heat transfer surface. For oscillatory flows, the heat transfer coefficients can be improved by using curved-liked surface such as spiral coil instead of straightlike surface such as fin coil. The relationships between the oscillating heat transfer coefficients at the heat exchangers, drive ratios, and operating frequencies are also presented. Higher drive ratios and operating frequency result in greater heat transfer coefficients.

Effect of γ-Al2O3/Water Nanofluid on Heat Transfer and Pressure Drop Characteristics of Shell and Coil Heat Exchanger With Different Coil Curvatures

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
M. R. Salem ◽  
R. K. Ali ◽  
R. Y. Sakr ◽  
K. M. Elshazly
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Pure Water ◽  
Average Increase ◽  
Average Size ◽  
Coil Heat Exchanger ◽  
Fanning Friction Factor ◽  
Coil Heat

This study presents an experimental investigation of the characteristics of convective heat transfer in horizontal shell and coil heat exchangers in addition to the friction factor for fully developed flow through their helically coiled tube (HCT). Five heat exchangers of counterflow configuration were constructed with different HCT-curvature ratios (δ) and tested at different mass flow rates and inlet temperatures of γ-Al2O3/water nanofluid in the HCT. The tests were performed for γ-Al2O3 with average size of 40 nm and particles volume concentration (ϕ) from 0% to 2% for 0.0392≤δ≤0.1194. Totally, 750 test runs were performed from which the HCT-average Nusselt number (Nu¯t) and fanning friction factor (fc) were calculated. Results illustrated that Nu¯t and fc of nanofluids are higher than those of the pure water at same flow condition, and this increase goes up with the increase in ϕ. When ϕ increases from 0% to 2%, the average increase in Nu¯t is of 59.4–81% at lower and higher HCT-Reynolds number, respectively, and the average increase in fc is of 25.7% and 27.4% at lower and higher HCT-Reynolds number, respectively, when ϕ increases from 0% to 2% for δ=0.1194. In addition, results showed that Nu¯t and fc increase by increasing coil curvature ratio. When δ increases from 0.0392 to 0.1194 for ϕ=2%, the average increase in Nu¯t is of 130.2% and 87.2% at lower and higher HCT-Reynolds number, respectively, and a significant increase of 18.2–7.5% is obtained in the HCT-fanning friction factor at lower and higher HCT-Reynolds number, respectively. Correlations for Nu¯t and fc as a function of the investigated parameters are obtained.

Convective Electronic Device Cooling Using Microencapsulated Phase Change Material Slurry in Planar Spiral Coil

2015 ◽  
Author(s):  
Houman B. Rokni ◽  
Ehsan M. Languri ◽  
Wayne Johnson
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermal Management ◽  
Carrying Capacity ◽  
Single Phase ◽  
Spiral Coil ◽  
Management Techniques ◽  
Spiral Coils ◽  
Change Material ◽  
Coil Heat

The current trend in miniaturization of electronic devises requires more effective thermal management techniques to remove the heat to ensure the maximum performance of the devise. Among all available thermal management techniques for electronic cooling, convective heat transfer cooling has gained attentions due to low cost and maturity in the market. The single-phase convective heat removal technique suffers from the low heat carrying capacity since there is no phase change occurs during the process. On the other hand, Microencapsulated phase change materials (MPCMs) are gaining attention due to their high heat carrying capacity. MPCMs are composed of phase change material (PCM) as the core material that is encapsulated with micrometer size shell materials. The PCM inside the capsules may undergo a phase change as the temperature varies around the melting and freezing temperature points of the PCM. This leads to a significant heat gain/release due to the phase change of the PCM. In this paper, we are performing a numerical modeling on the performance of MPCMs mixed with single-phase base fluid when pumped through planar spiral coils. From electronic thermal management point of view, it is ideal to have an enhanced coolant that maintain the operating temperature under an allowable level uniformly. The behavior of MPCM slurry when pumped through planar spiral coils reveals unique patterns due to the centrifugal forces. The available data on MPCM slurry through spiral coil heat exchangers show the new patterns of velocity and heat transfer curves that require further investigation and scientific explanations. The current paper studies the steady conditions of flows under laminar regimes at different boundary conditions. A CAD model of a planar coil heat exchanger is developed in SolidWorks. The model is meshed and discretized in order to apply the governing equations into the model. ANSYS Fluent package is used to solve the fluid flow and heat transfer equations inside the geometry. The velocity and temperature profiles along the coil are studied and discussed to quantify the roles of different forces in such flows. The ultimate goal of this study to evaluate the efficacy of utilizing such formulated microencapsulated PCM slurry at different mass concentrations on electronic thermal management considering the cost associated to the added pressure drop when using MPCM slurry.

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