Etude numerique et experimentale de la performance in regime transitoire de pompes a chaleur eau -air en cyclage

This study deals with water-to-air heat pumps (WAHP).; A literature review revealed that WARP models found in energy simulation programs are unable to correctly reproduce the real practical operation of these systems. The present study proposes a dynamic model that will allow more realistic WAHP simulations. This objective involves three main steps: (1) develop a detailed dynamic model of the HP; (2) validate this model experimentally; and (3) use this validated model to derive a simplified dynamic model for a direct implementation into energy simulation programs.; The studied WAHP has a standard configuration found in manufacturers' catalogs: a fin and tube refrigerant-to-air heat exchanger, a double tube refrigerant-to-water heat exchanger with the refrigerant flowing in the annulus and a fluted inner tube, a hermetic reciprocating compressor, a thermostatic expansion valve, a reversing valve, and R22 as the refrigerant.; In the exchangers, transient refrigerant flow is modelled with the mass, momentum, and energy conservation equations. Various correlations for heat transfer, pressure drop and void fraction are used. The refrigerant flows as a single phase fluid (liquid or vapour) or as a two-phase fluid. The fin and tube heat exchanger has a complex circuitry. To account for the various configurations of this heat exchanger, an indexation process was proposed. The model considers the fact that the refrigerant may be flowing or not (off-cycle). The finite volume method of Patankar, in conjunction with the Thomas Algorithm (TDMA), is used to numerically solve the system of equations resulting from the modelling.; The dynamic model of the hermetic reciprocating compressor is split into three parts: (i) evolution of the refrigerant in the crankcase, (ii) evolution of the refrigerant in the discharge tubing, and (iii) thermodynamic analysis of the compression process in the cylinders leading to the evaluation of the refrigerant flow rate and of the theoretical work for gas compression. The compression and the expansion of the gas in the cylinders are supposed to be polytropic.; The dynamic model of the thermostatic expansion valve also comprises three parts: (i) thermodynamic state of the bulb content; (ii) refrigerant flow in the open valve; and (iii) flow of refrigerant in the "closed" valve. For the latter case, the refrigerant uses the bleed port as a flowing passage. This bleed port was modelled with the conservation equations for two-phase flow. The refrigerant at the entrance of the bleed port may be in the liquid state (usual case), but also in two-phase or even in the vapour stale. The bleed port flow model is experimentally validated with data from the literature.; We also modelled the effects of the reversing valve and of the thermal mass in the plenum where the HP fan is located. Put together, these individual models form the global HP model. The global model uses an iterative algorithm that uses the refrigerant flow rates given by the individual models to find the condensation and boiling pressures, and then the conditions of the secondary fluids (air and liquid).; An experimental validation, the second main component of this work, completes the development of the HP model.; The validated model is finally used to simulate a HP working in various realistic conditions in order to derive a simplified model that is implemented in the energy simulation program TRNSYS. The major finding here is that, contrary to the impression coming from a consultation of the literature, the time constant attached to HP for the modelling of the evolution of their start-up capacity is dependent on the operating conditions. This represents a weakness of models found in simulation programs that are based on a fixed time constant. (Abstract shortened by UMI.)...