Measurement of Heat Transfer Coefficients for Non-Azeotropic Hydrocarbon Mixtures at Cryogenic Temperatures

2004 ◽  
Author(s):  
Cory B. Hughes ◽  
Gregory F. Nellis ◽  
John M. Pfotenhauer
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Circular Cross Section ◽  
Small Scale ◽  
Hydrocarbon Mixture ◽  
Cryogenic Temperatures ◽  
Hydrocarbon Mixtures ◽  
Experimental Apparatus

The use of non-azeotropic hydrocarbon mixtures in throttle-cycle refrigeration systems has resulted in large increases in the performance of Joule-Thomson type cryocoolers. However, there is very little data or theory currently available in the literature regarding the thermal-fluid behavior of multi-component, multi-phase mixtures at cryogenic temperatures. The design of these systems is therefore semi-empirical, relying heavily on experimental iteration. In this paper, an experimental apparatus is described that is capable of making precise and controlled measurements of the heat transfer coefficient over a range of cryogenic temperatures, compositions, geometries, and flow rates that are relevant to small-scale, throttle-cycle refrigeration systems. The experimental apparatus is used to carry out a study of the horizontal flow boiling heat transfer coefficient for a non-azeotropic hydrocarbon mixture in a circular cross-section with a constant wall temperature. The measurements are carried out over a range of cryogenic temperatures and the data is presented in the form of heat transfer coefficient as a function of temperature and thermodynamic quality. The experimental uncertainty of the measurements is theoretically estimated to be 10%. Measurements of the single-phase heat transfer coefficient for pure nitrogen fall within 10% of the Dittus-Boelter correlation.

scholarly journals Experimental investigation of subcooled flow boiling of water/TiO2 nanofluid in a horizontal tube

2016 ◽  
Vol 20 (1) ◽  
pp. 99-108 ◽  
Author(s):  
Hossein Rajabnia ◽  
Ehsan Abedini ◽  
Ali Tahmasebi ◽  
Amin Behzadmehr
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Flow Boiling ◽  
Horizontal Tube ◽  
Subcooled Flow Boiling ◽  
Boiling Regime ◽  
Subcooled Flow ◽  
Experimental Apparatus

Subcooled flow boiling heat transfer of water/TiO2 nanofluid in a horizontal tube is experimentally investigated. To validate the experimental apparatus as well as the experimental procedure, data for distilled water were compared with the available results on the literature in both single phase and subcooled flow boiling regime. Experimental investigations were carried out at three nanoparticles volumetric concentrations of 0.01%, 0.1%, and 5%. It was found that the nanofluid heat transfer coefficient in single-phase flow regime augments with the nanoparticle concentration. However, in the case of subcooled flow boiling regime the heat transfer coefficient decreases with the nanoparticle volume fractions.

Flow Boiling Inside a Single Circular Minichannel: Measurement of Local Heat Transfer Coefficient

2007 ◽  
Author(s):  
Alberto Cavallini ◽  
Stefano Bortolin ◽  
Davide Del Col ◽  
Marko Matkovic ◽  
Luisa Rossetto
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Experimental Apparatus ◽  
Boiling Process

This paper describes a new experimental apparatus for the measurement of the local heat transfer coefficient during flow boiling inside a 0.96 mm internal diameter single round cross section minichannel and reports preliminary heat transfer data taken during flow boiling of R134a. As a peculiar characteristic of the present technique, the heat transfer coefficient is not measured by imposing the heat flux; instead, the boiling process is governed by controlling the inlet temperature of the heating secondary fluid. This paper also presents a methodology to determine the critical conditions during the flow boiling process when no heat flux is imposed.

A Photographic Study of Flow Boiling Stability on a Plain Surface With Tapered Manifold

2015 ◽  
Author(s):  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Speed ◽  
Flow Boiling ◽  
High Heat ◽  
Bubble Nucleation ◽  
High Heat Transfer ◽  
Plain Surface ◽  
High Heat Transfer Coefficient

Flow boiling in microchannels offers many advantages such as high heat transfer coefficient, higher surface area to volume ratio, low coolant inventory, uniform temperature control and compact design. The application of these flow boiling systems has been severely limited due to early critical heat flux (CHF) and flow instability. Recently, a number of studies have focused on variable flow cross-sectional area to augment the thermal performance of microchannels. In a previous work, the open microchannel with manifold (OMM) configuration was experimentally investigated to provide high heat transfer coefficient coupled with high CHF and low pressure drop. In the current work, high speed images of plain surface using tapered manifold are obtained to gain an insight into the nucleating bubble behavior. The mechanism of bubble nucleation, growth and departure are described through high speed images. Formation of dry spots for both tapered and uniform manifold geometry is also discussed.

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