Experimental study and modeling of a H2O/NH3/H2 solar diffusion-absorption refrigerator for vaccine storage in regions without electrification
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Universidade Federal de Minas Gerais
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The objective of this work is to present a distributed condenser steady state mathematical model, written in
Python language, of a H2O/NH3/H2 diffusion and absorption fridge for vaccine storage in regions without electrification.
The refrigerator thermal input in ammonia vapor generator set was originally promoted by Joule effect through an 80.7
W electrical resistance. To supply the system with solar energy, the resistor is going to be replaced by a coaxial heat
exchanger, in which thermal oil heated in a solar concentrator flows in annular space of the outer tube. Condenser, generator and rectifier models were based on the energy, mass balance equations applications for ammonia and water and
the energy balance equation application for heat exchangers walls. Condenser input variables were obtained through peripheral components models. Thus, the ammonia mass flow rate and enthalpy at condenser inlet derive from generator set
model, as well as the output mass flow rate resulting from Bernoulli’s equation application, corrected for viscous effects,
for ammonia flow along the pipe that connects condenser and evaporator. Total system operating pressure that does not
vary spatially is the main model output variables. This variable is the result of a series of convergences involving model’s
equations, one of which is based on ammonia flows equality at condenser inlet and outlet. Model simulations carried out
revealed that total single pressure is equal to 1477000 Pa (14.77 bar). In addition, the ammonia, ammonia/water solution, and wall temperature profiles were determined for these components. Finally, the model was validated by comparing
the calculated values and the experimental data obtained by measurements performed with thermocouples and infrared
thermography. Differences between theoretical and experimental values were a maximum of 6.1%.
Abstract
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Engenharia mecânica, Energia solar, Refrigeradores
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Diffusion absorption refrigerator, Solar energy, Modeling, Vaccine storage, Heat transfer
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https://eventos.abcm.org.br/cobem2023/