Effect of operating conditions on the performance of the bubble pump of absorption-diffusion refrigeration cycles

Abstract

The mathematical model will be able to predict the operated condition (required tube diameters, heat input and submergence ratio….). That will result in a successful bubble pump design and hence a refrigeration unit. In the present work a one-dimensional two-fluid model of boiling mixing ammonia-water under constant heat flux is developed. The present model is used to predict the outlet liquid and vapor velocities and pumping ratio for different heat flux input to pump. The influence of operated conditions such as: ammonia fraction in inlet solution and tube diameter on the functioning of the bubble pump is presented and discussed. It was found that, the liquid velocity and pumping ratio increase with increasing heat flux, and then it decreases. Optimal heat flux depends namely on tube diameter variations. Vapour velocity increases linearly with increasing heat flux under designed conditions

Computational fluid dynamics parametric investigation for two-phase flow of ammonia-water mixing in bubble pump tube

“…The velocity slip with the heat flux, 2.83 kW/m 2 using water as the working fluid is 0.3 m/s [14] and in the current study, the corresponding value is 0.317m/s. The void fraction at 20 kW/m 2 in the study using ammonia/water [13] is 0.98 and in the present study is 0.94. The variation is only 4-6% with the present model and hence the validation is acceptable.…”

“…Increasing heat flux for a fixed time or increasing the time of heating leads to increase the amount of heat received by the mixing flow. By refereeing to void fraction values, flow patterns are defined as a bubbly flow for a void fraction less than 0.3, slug flow for void fraction between 0.3 and 0.55, churn flow for void fraction between 0.55 and 0.8 and annular flow for a void fraction more than 0.8 [13]. By examining the different contours at the different time and different heat flux, we can realise the important results.…”

“…The two-fluid model in steady state conditions and a correlation of optimum heat transfer as a function of mass flux and tube diameter is obtained using ammonia/water two-phase flow [10,11]. The lengths of the different zone of flow patterns along the bubble pump tube for different heat transfer and tube diameter and the maximum pumping ratio of 0.35 are defined [12,13]. A simulation of a uniformly heated tube of bubble pump employing the boiling flow and interfacial transport models and the liquid and vapour velocity profiles were similar to earlier reports [14].…”

Design Analysis and Fabrication of Solar Vapour Absorption

“…Hence, solar energy is the most promising unconventional energy sources. Solar energy has many factors in its favor with respect to availability, green environment and renewability [2][3][4]. This work involves operate refrigeration system with the use of solar energy.…”

Modeling of Boiling Two-Phase Flow in the Bubble Pump of Diffusion-Absorption Refrigeration Cycles

“…Benhmidene et al (2011a) investigated the optimization of the heat flux density received by a bubble pump and correlated the minimum heat flux density for pumping a water-ammonia solution as a function of the tube diameter of the bubble pump and mass flow rate of the two-phase flow. In addition, Benhmidene et al (2011b) studied the influence of the operating conditions such as the tube diameter, pressure, and ammonia mass fraction in the solution at the bubble pump entrance on the flow parameters at the bubble pump exit. The authors concluded that tube diameter is the parameter that influences the bubble pump operation the most.…”