Experiments are carried out on a bubble absorber, operating as part of a vapour absorption refrigeration system working with HCFC22-DMF to obtain heat and mass transfer and pressure drop data. The results are evaluated to obtain the dependence of absorption process on different parameters. Experimental data are compared with the numerical correlation relating Sherwood number, Reynolds number, Schmidt number and length to diameter ratio developed earlier by the authors. Also the experimental pressure drop is compared with the pressure drop obtained from other well known classical correlations and the numerical model.Experiments are carried out on a bubble absorber, operating as part of a vapour absorption refrigeration system working with HCFC22-DMF to obtain heat and mass transfer and pressure drop data. The results are evaluated to obtain the dependence of absorption process on different parameters. Experimental data are compared with the numerical correlation relating Sherwood number, Reynolds number, Schmidt number and length to diameter ratio developed earlier by the authors. Also the experimental pressure drop is compared with the pressure drop obtained from other well known classical correlations and the numerical model.

A Mani

Department of Mechanical Engineering

Absorption

Bubbles (in fluids)

Heat transfer

MASS TRANSFER

Mathematical models

Pressure drop

Refrigerants

Reynolds number

BUBBLE ABSORBER

SCHMIDT NUMBER

SHERWOOD NUMBER

VAPOR ABSORPTION REFRIGERATION SYSTEM

Refrigeration

BUBBLING SYSTEM

mathematical modeling

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IIT Madras

Experiments on a bubble absorber

International Communications in Heat and Mass Transfer

Experimental investigations have been carried out to study heat and mass transfer characteristics of Tetrafluoro ethane (R134a) in Dimethyl formamide (DMF) solution in a compact bubble absorber of vapour absorption refrigeration system of 1 TR capacity. Plate heat exchangers have been used as system components. Bubble absorption principle is employed in the absorber and hot water supplies heat to the generator. Effect of operating parameters such as circulation ratio, absorber and generator temperatures on heat and mass transfer effectiveness, overall heat transfer coefficient and volumetric mass transfer coefficient are investigated. It is found that heat and mass transfer effectiveness of absorber are better at lower circulation ratios and higher generator temperatures. Experimental results are compared with those obtained from numerical model developed earlier by the authors and the agreement is generally fair. From the experimental data, a correlation has been obtained for volumetric mass transfer coefficient, using multi-linear regression analysis. © 2012 Elsevier Ltd and IIR. All rights reserved.

International Journal of Refrigeration

Heat and mass transfer studies on a compact bubble absorber in R134a-DMF solution based vapour absorption refrigeration system

Experimental investigations have been carried out to visualize bubble behavior and effect of gas flow rate and liquid concentration on bubble characteristics of Tetrafluoro ethane (R134a) in liquid R134a-Dimethyl Formamide (DMF) solution in a glass absorber. Bubble behavior was studied in still as well as flowing solution. At lower gas flow rates, bubbles tend to be spherical due to the dominance of surface tension. At higher gas flow rates, bubbles tend to be hemispherical due to the dominance of inertia force. Bubble diameter during detachment increases with increase in gas flow rates. Also, the bubble diameter initially increases as the solution concentration increases up to 0.075kgkg -1 and then starts decreasing as the solution concentration increases further. At lower solution concentrations, effect of absorption driving potential (x eq-x l) is dominant than that of surface tension, due to this bubble diameter increases. When the solution concentration is increased further, effect of surface tension is dominant resulting in decrease in bubble diameter. Bubble diameter measured from the experiments is compared with that of the numerical model developed by the authors and other literature experimental correlations and it is found that the agreement is good. A correlation for bubble diameter during detachment is presented from the experimental studies, which can be useful for the design of R134a-DMF bubble absorber. © 2012 Elsevier Inc.

Experimental Thermal and Fluid Science

Experimental studies on bubble characteristics for R134a-DMF bubble absorber

Experimental investigations have been carried out to study heat and mass transfer characteristics of Tetrafluoro ethane (R134a) in Dimethyl formamide (DMF) in a glass absorber. Effects of operational parameters viz.; gas flow rate, solution flow rate, solution initial concentration, solution pressure, solution temperature and cooling water flow rate on absorber performance are analyzed. Absorption rate and heat transfer rate increase as the gas flow rate, solution flow rate, cooling water flow rate and solution pressure increase whereas they decrease as the solution initial concentration and solution temperature increase. Heat and mass transfer rates determined from the experiments are compared with numerical model and it is found that agreement is good. A correlation for mass transfer coefficient is presented from the experimental studies within ±20% error band. © 2012 Elsevier Ltd and IIR. All rights reserved.

Experimental studies on heat and mass transfer characteristics for R134a-DMF bubble absorber

A phenomenological theory of heat and mass transfer is applied to model the absorption of the R134a gas bubble in liquid R134a-dimethyl formamide (DMF) solution. Required properties of R134a-DMF liquid solution namely liquid density, surface tension, diffusion coefficient, thermal conductivity, specific heat, etc., have been calculated using experimental correlations. Results have been obtained by modeling on a computer using MATLAB. The bubble dynamics during bubble growth are studied using this model. Liquid concentration, temperature, heat and mass transfer rates, local heat and mass transfer coefficients are estimated at the bubble interface. Absorption rate, coupled heat transfer rate, average heat and mass transfer coefficients over the entire bubble life span are also calculated. This model results are validated using experimental results of ammonia-water solution. The maximum bubble radius determined from this study is compared with available experimental correlations and it is found that agreement is good. Heat and mass transfer rates obtained from this model are compared with the literature experimental results. The results are in good agreement with the predictions of the model. © 2010 Elsevier Ltd. All rights reserved.

International Journal of Heat and Mass Transfer

Heat and mass transfer studies on R134a bubble absorber in R134a/DMF solution based on phenomenological theory

International Journal of Numerical Methods for Heat and Fluid Flow

Finite element analysis of a bubble absorber

A model of the absorption process in a vertical tubular bubble absorber working with R22-DMF, R22-DMA, R22-DMETEG, R22-DMEDEG and R22-NMP is developed using finite element method employing Galerkin's technique. The objective of this paper is to study the influence of the liquid and gas properties on the volumetric mass transfer coefficient. Analysis have also been done using ammonia-water as working fluid, the results obtained are compared with those in the literature and the agreement is found to be good. A correlation for mass transfer coefficient is proposed as a function of Reynolds number, Schmidt number and length to diameter ratio. The correlation can be used either in estimating the mass transfer rates or in fixing up any of the major design parameters namely length required for complete absorption and diameter.

Heat and Mass Transfer/Waerme- und Stoffuebertragung

Analysis of a bubble absorber working with R22 and five organic absorbents

Prediction of transport properties of R22-DMF refrigerant-absorbent combinations

Heat and mass transfer in vertical tubular bubble absorbers for ammonia-water absorption refrigeration systems

Advances in Chemical Engineering

Properties of Cocurrent Gas-Liquid Flow

Journal	Data powered by TypesetInternational Communications in Heat and Mass Transfer
Publisher	Data powered by TypesetElsevier Science Ltd, Exeter, United Kingdom
ISSN	07351933
Open Access	No