The amount of water required to decrease the critical temperature difference of a standing wave thermoacoustic engine

Thermocapillary convection in a shallow annular pool (depth d = 1 mm) of silicone oil (0.65 cSt, Pr = 6.7), heated from the inner wall, is investigated by numerical simulations. Under a fixed value of temperature difference between the outer and inner walls, surface temperature gradient in the inner heated pool is about 10% higher than that in the outer heated pool. Accordingly, the critical temperature difference for the incipience of HTW (ΔTc = 4.58K) is smaller than that (ΔTc = 5.0K) in the outer heated pool. Numerical simulations indicate that two groups of HTW, propagating in opposite azimuthal directions to each other, coexist and produce interference patterns in the inner heated pool. Rotation of the pool around its axis gives no significant influence on the behavior of HTW in the inner heated pool. The characteristics of HTW are discussed in contrast with those in the outer heated pool.

Download Full-text

Thermal delay of drop coalescence

Journal of Fluid Mechanics ◽

10.1017/jfm.2017.686 ◽

2017 ◽

Vol 833 ◽

Cited By ~ 14

Author(s):

Michela Geri ◽

Bavand Keshavarz ◽

Gareth H. McKinley ◽

John W. M. Bush

Keyword(s):

Critical Temperature ◽

Residence Time ◽

Temperature Difference ◽

Initial Temperature ◽

Theoretical Study ◽

Fluid Viscosity ◽

Drop Coalescence ◽

Thermocapillary Flows ◽

Silicone Oils ◽

Thermal Delay

We present the results of a combined experimental and theoretical study of drop coalescence in the presence of an initial temperature difference $\unicode[STIX]{x0394}T_{0}$ between a drop and a bath of the same liquid. We characterize experimentally the dependence of the residence time before coalescence on $\unicode[STIX]{x0394}T_{0}$ for silicone oils with different viscosities. Delayed coalescence arises above a critical temperature difference $\unicode[STIX]{x0394}T_{c}$ that depends on the fluid viscosity: for $\unicode[STIX]{x0394}T_{0}>\unicode[STIX]{x0394}T_{c}$, the delay time increases as $\unicode[STIX]{x0394}T_{0}^{2/3}$ for all liquids examined. This observed dependence is rationalized theoretically through consideration of the thermocapillary flows generated within the drop, the bath and the intervening air layer.

Download Full-text

The Influence of Stack Position and Acoustic Frequency on the Performance of Thermoacoustic Refrigerator with the Standing Wave

Archives of Thermodynamics ◽

10.1515/aoter-2017-0026 ◽

2017 ◽

Vol 38 (4) ◽

pp. 89-107 ◽

Cited By ~ 2

Author(s):

Jakub Kajurek ◽

Artur Rusowicz ◽

Andrzej Grzebielec

Keyword(s):

Standing Wave ◽

Temperature Difference ◽

Heat Exchangers ◽

Acoustic Power ◽

Working Fluid ◽

Parallel Plates ◽

Acoustic Frequency ◽

Plate Spacing ◽

Resonance Frequencies ◽

Thermoacoustic Refrigerator

Abstract Thermoacoustic refrigerator uses acoustic power to transport heat from a low-temperature source to a high-temperature source. The increasing interest in thermoacoustic technology is caused due to its simplicity, reliability as well as application of environmentally friendly working fluids. A typical thermoacoustic refrigerator consists of a resonator, a stack of parallel plates, two heat exchangers and a source of acoustic wave. The article presents the influence of the stack position in the resonance tube and the acoustic frequency on the performance of thermoacoustic refrigerator with a standing wave driven by a loudspeaker, which is measured in terms of the temperature difference between the stack edges. The results from experiments, conducted for the stack with the plate spacing 0.3 mm and the length 50 mm, acoustic frequencies varying between 100 and 400 Hz and air as a working fluid are consistent with the theory presented in this paper. The experiments confirmed that the temperature difference for the stack with determined plate spacing depends on the acoustic frequency and the stack position. The maximum values were achieved for resonance frequencies and the stack position between the pressure and velocity node.

Download Full-text