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.

An Experimental Study of Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry in a Coil Heat Exchanger

2013 ◽  
Author(s):  
Minsuk Kong ◽  
Jorge L. Alvarado ◽  
Ehsan M. Languri
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Coil Heat Exchanger ◽  
Change Material ◽  
Coil Heat

The use of microencapsulated phase change material (MPCM) slurry as an enhanced heat transfer fluid is considered to be very promising for saving energy in thermal energy systems. However, little is known how MPCM may exhibit enhanced heat transfer performance in coil heat exchanger. Coil heat exchangers are extensively used in industrial applications including heating, ventilating and air conditioning (HVAC) systems because of their superior heat transfer performance and compactness. In this study, the heat transfer characteristics of MPCM slurry in a coil heat exchanger have been investigated experimentally. Thermal properties of MPCM slurry were measured using a differential scanning calorimeter. Pressure drop, overall heat transfer coefficient and heat transfer effectiveness in a coil heat exchanger were determined by considering different flow rates. It was found that heat transfer characteristics were positively affected by the phase change process of the phase change material in MPCM, even though MPCM exhibit reduced turbulence and increased pressure drop. The overall heat transfer coefficient for MPCM slurry is in the range of 5,000 to 9,000 W/m2-K over a Dean number range from 1,600 to 4,000 (equivalent Reynolds number range of 6,000 to 15,000). The enhancement in heat transfer performance is about 17% when compared to that for water. In addition, durability tests of MPCM slurry were conducted to evaluate the MPCM’s ability to withstand continuous pumping conditions, which is critically important in the implementation of MPCM slurry in industrial applications.

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.

Sign in / Sign up

Export Citation Format

Share Document