Thermodynamic Foundations of Working Processes in Positive-Displacement Machines Designed for Compression of Two-Phase, Two-Component Working Fluids

2019 ◽  
Vol 55 (5-6) ◽  
pp. 463-472
Author(s):  
V. E. Shcherba ◽  
V. V. Shalai ◽  
A. V. Zanin
Keyword(s):  
Two Phase ◽  
Working Fluids ◽  
Positive Displacement ◽  
Two Component ◽  
Working Processes

An Analytical and Experimental Study of Rotary-Vane Turbomachinery: Single-Phase Working Fluids

2008 ◽  
Author(s):  
A. Mehdizadeh ◽  
A. M. Mahmoud ◽  
S. A. Sherif ◽  
W. E. Lear
Keyword(s):  
Single Phase ◽  
Volume Ratio ◽  
Industrial Applications ◽  
Design Tool ◽  
Low Flow ◽  
Geometrical Parameters ◽  
Two Phase ◽  
Working Fluids ◽  
Positive Displacement ◽  
Air Compression

Rotary machines have played an important role for many years in refrigeration and air compression applications because of their inherent simplicity and reliability. They are also very attractive machines since as positive displacement devices; they are more suitable for low flow rates (low specific speeds). In this paper, the thermodynamic and fluid mechanic characteristics of a rotary-vane air-motor are analyzed. The optimum geometrical and operational characteristics of the machine are presented. Experiments are conducted to understand the working principles and operational constraints of the machine. This study also helps formulate design procedures that can be utilized to modify air-motors into optimized expanders for single-phase flow applications. The model has been used to evaluate geometrical parameters such as the optimum intake and exhaust port locations, their spreads and the geometric volume ratio, as well as evaluating performance parameters such as the work produced and the mechanical, isentropic and total efficiencies of the machine. It is anticipated in a follow-up study that the model developed will be the basis for an expander design tool that uses two-phase working fluids in relevant industrial applications.

Converting Low-Grade Heat Into Power Using a Supercritical Rankine Cycle With Zeotropic Mixture Working Fluid

2010 ◽  
Author(s):  
Huijuan Chen ◽  
D. Yogi Goswami ◽  
Muhammad M. Rahman ◽  
Elias K. Stefanakos
Keyword(s):  
Rankine Cycle ◽  
Phase Region ◽  
Working Fluid ◽  
Condensation Process ◽  
Heating Process ◽  
Low Grade ◽  
Two Phase ◽  
Working Fluids ◽  
Zeotropic Mixture ◽  
Low Grade Heat

A supercritical Rankine cycle using zeotropic mixture working fluids for the conversion of low-grade heat into power is proposed and analyzed in this paper. A supercritical Rankine cycle does not go through two-phase region during the heating process. By adopting zeotropic mixtures as the working fluids, the condensation process happens non-isothermally. Both of the features create a potential in reducing the irreversibility and improving the system efficiency. A comparative study between an organic Rankine cycle and the proposed supercritical Rankine cycle shows that the proposed cycle improves the cycle thermal efficiency, exergy efficiency of the heating and the condensation processes, and the system overall efficiency.

scholarly journals EXCHANGE COUPLING AND ENHANCEMENT OF CURIE TEMPERATURE OF THE INTERGRANULAR AMORPHOUS REGION IN NANO-CRYSTALLINE DUPLEX-PHASE ALLOYS SYSTEM

2007 ◽  
Vol 21 (27) ◽  
pp. 4689-4706
Author(s):  
Y. Z. SHAO ◽  
W. R. ZHONG ◽  
G. M. LIN ◽  
X. D. HU
Keyword(s):  
Curie Temperature ◽  
Exchange Coupling ◽  
Volume Fraction ◽  
Amorphous Region ◽  
Experimental Result ◽  
Dual Phase ◽  
Two Phase ◽  
Nanocrystallite Size ◽  
Nano Crystalline ◽  
Two Component

We studied the theoretical Curie temperature of a dual-phase nanomagnetic system by Monte Carlo simulation of a modified Heisenberg model on a 3D complex lattice consisting of single- and cluster-spins. We also systematically investigated the experimental Curie temperature of a dual-phase nanomagnetic alloy and performed a direct comparison between theory and experiment. The exchange coupling between two component magnetic phases substantially affects the Curie temperature [Formula: see text] of the intergranular amorphous region of a dual-phase nanomagnetic system. The [Formula: see text] depends upon the nanocrystallite size d, the volume fraction Vc and the interspace among crystallites ξ. Large crystallized volume fraction Vc, small grain size d, and thin interphase thickness ξ lead to an obvious enhancement of Curie temperature (ECT) of intergranular amorphous region, whereas the Curie temperature of nanocrystallites [Formula: see text] decreases slightly. By simulation, we worked out a relationship between the reduced ECT and ξ, as [Formula: see text], and it conforms to the experimental result. In addition, we also simulated the demagnetization of a hard–soft nanocomposite system. The exchange coupling between two component phases affects the cooperativity of two-phase magnetizations, the coherent reversal of magnetizations, and coercivity.

scholarly journals Generalized second-order slip for unsteady convective flow of a nanofluid: a utilization of Buongiorno’s two-component nonhomogeneous equilibrium model

2020 ◽  
Vol 9 (1) ◽  
pp. 156-168
Author(s):  
Seyed Mahdi Mousavi ◽  
Saeed Dinarvand ◽  
Mohammad Eftekhari Yazdi
Keyword(s):  
Boundary Layer ◽  
Equilibrium Model ◽  
Second Order ◽  
Model Parameters ◽  
Slip Parameter ◽  
Two Phase ◽  
Convective Boundary ◽  
First Order ◽  
Special Cases ◽  
Two Component

AbstractThe unsteady convective boundary layer flow of a nanofluid along a permeable shrinking/stretching plate under suction and second-order slip effects has been developed. Buongiorno’s two-component nonhomogeneous equilibrium model is implemented to take the effects of Brownian motion and thermophoresis into consideration. It can be emphasized that, our two-phase nanofluid model along with slip concentration at the wall shows better physical aspects relative to taking the constant volume concentration at the wall. The similarity transformation method (STM), allows us to reducing nonlinear governing PDEs to nonlinear dimensionless ODEs, before being solved numerically by employing the Keller-box method (KBM). The graphical results portray the effects of model parameters on boundary layer behavior. Moreover, results validation has been demonstrated as the skin friction and the reduced Nusselt number. We understand shrinking plate case is a key factor affecting non-uniqueness of the solutions and the range of the shrinking parameter for which the solution exists, increases with the first order slip parameter, the absolute value of the second order slip parameter as well as the transpiration rate parameter. Besides, the second-order slip at the interface decreases the rate of heat transfer in a nanofluid. Finally, the analysis for no-slip and first-order slip boundary conditions can also be retrieved as special cases of the present model.

Heat Transport Characteristics in Closed Loop Oscillating Heat Pipes

2005 ◽  
Author(s):  
Shuangfeng Wang ◽  
Shigefumi Nishio
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Closed Loop ◽  
Flow Behavior ◽  
Working Fluid ◽  
Liquid Volume ◽  
High Heat Flux ◽  
Two Phase ◽  
Working Fluids ◽  
Inner Diameter

Heat transport rates of micro scale SEMOS (Self-Exciting Mode Oscillating) heat pipe with inner diameter of 1.5mm, 1.2mm and 0.9mm, were investigated by using R141b, ethanol and water as working fluids. The effects of inner diameter, liquid volume faction, and material properties of the working fluids are examined. It shows that the smaller the inner diameter, the higher the thermal transport density is. For removing high heat flux, the water is the most promising working fluid as it has the largest critical heat transfer rate and the widest operating range among the three kinds of working fluids. A one-dimensional numerical simulation is carried out to describe the heat transport characteristics and the two-phase flow behavior in the closed loop SEMOS heat pipe. The numerical prediction agrees with the experimental results fairly well, when the input heat through was not very high and the flow pattern was slug flow.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.

Sign in / Sign up

Export Citation Format

Share Document