Ammonia/Ethanol Mixture for Adsorption Refrigeration

Mauro Luberti,Giulio Santori,Chiara Di Santis

doi:10.3390/en13040983

Mauro Luberti, Giulio Santori + Show 1 more

Open Access

https://doi.org/10.3390/en13040983

Copy DOI

Journal: Energies	Publication Date: Feb 22, 2020
Citations: 12	License type: CC BY 4.0

Affiliation: University of Edinburgh

Abstract

Adsorption refrigeration has become an attractive technology due to the capability to exploit low-grade thermal energy for cooling power generation and the use of environmentally friendly refrigerants. Traditionally, these systems work with pure fluids such as water, ethanol, methanol, and ammonia. Nevertheless, the operating conditions make their commercialization still unfeasible, especially owing to safety and cost issues as a consequence of the working pressures, which are higher or lower than 1 atm. The present work represents the first thermodynamic insight in the use of mixtures for adsorption refrigeration and aims to assess the performance of a binary system of ammonia and ethanol. According to the Gibbs’ phase rule, the addition of a component introduces an additional degree of freedom, which allows to adjust the pressure of the system varying the composition of the mixture. The refrigeration process was simulated with isothermal- isochoric flash calculations to solve the phase equilibria, described by the Peng-Robinson-Stryjek-Vera (PRSV) equation of state for the vapor and liquid phases and by the ideal adsorbed solution theory (IAST) and the multicomponent potential theory of adsorption (MPTA) for the adsorbed phase. In operating condenser and evaporator, pressure levels around atmospheric pressure can be achieved using an ammonia/ethanol mixture with a mole fraction of ethanol in the range of 0.70−0.75. A good agreement in the predictions of the adsorbed phase composition was also reported using the IAST and the MPTA methods.

Highlights

The growing awareness of global warming and the need for reducing carbon emissions has resulted in incentives to fully develop renewable energy conversion technologies including refrigeration and air conditioning [1]
In a recent study by Santori and Di Santis [9], performances of the thermodynamic cycle were related to the fluid critical temperature (Tcr ), critical pressure (Pcr ), critical density, acentric factor (ω), and molar heat capacity of ideal gas at critical point. This approach confirmed the advantage of using traditional fluids for adsorption refrigeration and showed that other fluids, such as isopropanol, have promising properties, anticipating values of coefficient of performance (COP) not far from ethanol and methanol (Table 1)
In case study B, multiple cycles were run until the convergence of the pressures in the condenser and in the the multicomponent potential theory of adsorption (MPTA) was implemented [18] focusing only on evaporator was achieved

Summary

Introduction

The growing awareness of global warming and the need for reducing carbon emissions has resulted in incentives to fully develop renewable energy conversion technologies including refrigeration and air conditioning [1]. In a recent study by Santori and Di Santis [9], performances of the thermodynamic cycle were related to the fluid critical temperature (Tcr ), critical pressure (Pcr ), critical density (ρcr ), acentric factor (ω), and molar heat capacity of ideal gas at critical point (cp 0 ,cr ). This approach confirmed the advantage of using traditional fluids for adsorption refrigeration and showed that other fluids, such as isopropanol, have promising properties, anticipating values of coefficient of performance (COP) not far from ethanol and methanol (Table 1).

Thermodynamic Model

A: Complete cycle modelling with

Case Study B

Case Study A

Evolution

Coefficient

Conclusion