Binary-Fluid Heat and Mass Transfer in Microchannel Geometries for Miniaturized Thermally Activated Absorption Heat Pumps

2006 ◽  
pp. 339-368 ◽  
Author(s):  
Srinivas Garimella
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Pumps ◽  
Binary Fluid ◽  
Thermally Activated

Experimental study of 3D – structured adsorbent composites with improved heat and mass transfer for adsorption heat pumps

2021 ◽  
pp. 133365
Author(s):  
Marc Scherle ◽  
Timothy A. Nowak ◽  
Stefan Welzel ◽  
Bastian J.M. Etzold ◽  
Ulrich Nieken
Keyword(s):  
Mass Transfer ◽  
Experimental Study ◽  
Heat And Mass Transfer ◽  
Heat Pumps ◽  
Adsorption Heat

Design of Microscale Heat and Mass Exchangers for Absorption Space Conditioning Applications

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Ananda Krishna Nagavarapu ◽  
Srinivas Garimella
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Flow Distribution ◽  
Mass Transfer Process ◽  
High Heat ◽  
Heat Pumps ◽  
Operating Conditions ◽  
Pressure Drops ◽  
Transfer Rates ◽  
Small Absorption

This paper presents the development of a miniaturization technology for heat and mass exchangers used in absorption heat pumps. The exchanger consists of an array of parallel, aligned alternating shims with integral microscale features, enclosed between cover plates. These microscale features facilitate the flow of the various fluid streams and the associated heat and mass transfer. In an absorber application, effective vapor and solution contact and microscale features for the flow of both the solution and the coolant induce high heat and mass transfer rates without any active or passive surface enhancement. The geometry ensures even flow distribution with minimal overall pressure drops. A model of the coupled heat and mass transfer process for ammonia-water absorbers using this configuration under typical operating conditions demonstrates the potential for extremely small absorption components. The proposed concept is compact, modular, versatile, and in an eventual implementation, can be mass produced. Additionally, the same concept can be extended to the other absorption heat pump components as well as for several other industries involved in multicomponent fluid processes.

scholarly journals Effects of the Hydro Anisotropy and the Magnetic Field on the Dynamic Thermo-Bi-Diffusive Flow in a Horizontal Cavity Confining a Porous Medium Saturated by a Binary Fluid

2021 ◽  
pp. 1-13
Author(s):  
Faras Issiako ◽  
Christian Akowanou ◽  
Macaire Agbomahena
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Porous Medium ◽  
Heat And Mass Transfer ◽  
Transverse Magnetic Field ◽  
Mass Transfer Rate ◽  
Transverse Magnetic ◽  
Binary Fluid ◽  
Diffusive Flow ◽  
Horizontal Cavity

We analyze analytically the effects of anisotropy in permeability and that of a transverse magnetic field on thermal convection in a porous medium saturated with a binary fluid and confined in a horizontal cavity. The porous medium, of great extension, is subjected to various conditions at the thermal and solutal boundaries. The axes of the permeability tensor are oriented obliquely with respect to the gravitational field. Based on a scale analysis, the velocity, temperature, and heat and mass transfer rate fields were determined. These results were validated by the study of borderline cases which are: pure porous media and pure fluid media discussed in the literature. It emerges from this study that the anisotropy parameters influence the convective flow. The application of a transverse magnetic field significantly reduces the speed of the flow and thereby affects the temperature field and the rate of heat and mass transfer.

The Role of Surfactant Adsorption Rate in Heat and Mass Transfer Enhancement in Absorption Heat Pumps

2000 ◽  
Author(s):  
Michael S. Koenig ◽  
Gershon Grossman ◽  
Khaled Gommed
Keyword(s):  
Mass Transfer ◽  
Surface Tension ◽  
Heat And Mass Transfer ◽  
Heat Pumps ◽  
Surfactant Adsorption ◽  
Relaxation Rates ◽  
Dynamic Surface ◽  
Vapor Interface ◽  
Enhanced Absorption ◽  
Liquid Vapor

Abstract The importance of heat and mass transfer additives in absorption chillers and heat pumps has been recognized for over three decades. However, a universally accepted model for the mechanisms responsible for enhanced absorption rates has yet to be proposed. The Marangoni effect — an instability arising from gradients in surface tension at the liquid-vapor interface — is generally accepted as the cause of the convective flows that enhance transfer rates. Certain surfactant additives can significantly improve absorption rates and thus reduce the overall transfer area required by a given machine. Any means available that can increase the efficiency and acceptability of absorption machines is to be welcomed, as this technology provides an alternative to vapor compression systems which is both environmentally friendly and more versatile with regards to energy sources. This study investigates the rate at which a surfactant additive adsorbs at a liquid-vapor interface. The residence time of the falling liquid solution in an absorber is quite short. An effective additive must not only reduce the surface tension of the solution; it must do so quickly enough to cause the Marangoni instability within the short absorption process time. The entrance region of an absorber features a freshly exposed interface at which no surfactant has adsorbed. A numerical model is used to analyze surfactant relaxation rates in a static film of additive-laced solution. Kinetic parameters for the combination of the working pair LiBr-H2O and the additive 2-ethyl-1-hexanol are derived from data in the literature for static and dynamic surface tension measurements. Bulk, interfacial and boundary parameters influencing relaxation rates are discussed for surfactant adsorption occurring in the absence of absorption, as well as for concurrent adsorption and stable vapor absorption. Initial solution conditions and absorption driving force are shown to impact the potential for instability in the effect they have on the rate of interfacial additive adsorption.

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