Abstract
The main objective of this work is to establish a detailed modelling technique to predict the refrigerant conditions such as pressure and enthalpy of a VC system. The transient state modelling techniques suggested in many research works are usually not easy to reproduce due to lack of detailed methodology and the multitude of analytical or computational schemes that could not be assessed objectively. This work has addressed this issue by introducing a modelling method developed from conservation equations of mass and energy represented with Navier–Stokes equations. A finite volume scheme has been used to discretize the governing equations along the heat exchanger models. Transient state modelling matrices have been established after dividing the condenser as well as the evaporator into 3 and n control volumes. The model validation with experiments was satisfactory. The model outputs such as the refrigerant pressure across the condenser and evaporator are in agreement with experiments. The proposed modelling technique could be adopted to predict optimal parameters during start-up. The modelling results could be used to design VC systems with optimal performance.
Highlights
Critical processes could be identified through modelling in order to draw key design requirements [1]
E data acquisition system is the RA1 software, and data logger is run by a Windows personal computer (PC). e software enables real-time control, and monitoring of all the measurement device outputs with a mimic diagram displayed on the PC screen
Low temperature refrigerant mixture enters the evaporator to be heated by surrounding water so that phase change to vapor could occur prior to returning to the compressor. e actual image of the experimental setup given in Figures 4 and 5 describes the refrigerant’s thermodynamic cycle in vapor compression (VC) systems
Summary
Critical processes could be identified through modelling in order to draw key design requirements [1]. Finite difference for PDE’s discretization was used and Gaussian elimination was adopted for solution tracking Parameters such as refrigerant pressure and temperature were predicted with the distributed model; numerical results were not validated with the experiments. Detailed transient state modelling was presented by [9] using a lumped parameter model to investigate the liquid, two-phase, and vapor zones in heat exchangers. E model-based approach was developed from first principles and was divided in 3 subcategories, namely, the finite control volume, moving boundary, and lumped parameters methods. E model-based approach required validation with the experiments and was later on detailed in [16] using finite volume and moving boundary methods to discuss benefits and limitations of both schemes.
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