000188160 001__ 188160
000188160 005__ 20190316235702.0
000188160 037__ $$aCONF 000188160 245__$$aDynamic Modeling and Simulation of Two-phase Evaporators and Condensers in the context of a CO2 Based District Energy Network
000188160 269__ $$a2013 000188160 260__$$c2013
000188160 336__ $$aConference Papers 000188160 520__$$aA new type of district energy network has recently been proposed that is based on the use of CO2 as a heat transfer fluid. It uses the latent heat of vaporization, instead of sensible heat, to store and transfer heat. Previous studies have focused on demonstrating the potential of such a network in terms of energy efficiency and economy. In order to assess the technical feasibility of such a network, and to address some of the safety related issues, an analysis of the network’s dynamics is required. Such an analysis requires models to be developed for the network’s central plant, heating users’ substations, cooling users’ substations, as well as for the piping. Moreover these dynamic models should be developed in such a way that they can be calibrated with the help of a future experimental setup. In this context a dynamic model of a plate evaporator (also useable as a plate condenser) is presented, it is based on a one dimensional local formulation of the conservation laws for mass, momentum and energy. In this formulation, mass and energy in the components are allowed to vary, while non stationary terms in the momentum equation are neglected. On the water side, frictional pressure drops are computed with Churchill equation while heat transfer coefficient is computed with Gnielinski’s correlation. On the refrigerant side, a constant friction factor was implemented, while heat transfer coefficient is set to a reference value at reference conditions of mass flux and pressure. Variations of the heat transfer coefficient due to changes with respect to these two conditions are handled with exponents. These values are to be calibrated experimentally in a future work. The thermal capacity due to the mass of construction material was also accounted for in the model. In order to select an appropriate control scheme to be used in the experimental facility and, later on in a real network, the behavior of a cooling user substation including a control valve and an evaporator is discussed. A proportional integral controller showed its ability to stabilize the system to a desired degree of superheat at the evaporator outlet. Finally, perturbation rejection tests were made, and showed the ability of the system to operate under changing conditions of CO2 pressure and inlet enthalpy, as well as changes in the water mass flowrate, and inlet enthalpy.
000188160 6531_ $$aDynamic modeling 000188160 6531_$$aDynamic simulation
000188160 6531_ $$aEvaporator 000188160 6531_$$aCondenser
000188160 6531_ $$aControl 000188160 700__$$0244600$$g167324$$aHenchoz, Samuel
000188160 700__ $$0240374$$g140973$$aMaréchal, François 000188160 700__$$0240152$$g105085$$aFavrat, Daniel
000188160 7112_ $$dJuly 16-19, 2013$$cGuilin, PRC$$aECOS 2013 000188160 8564_$$uhttps://infoscience.epfl.ch/record/188160/files/B015final.pdf$$zn/a$$s948332$$yn/a 000188160 909C0$$xU12691$$0252481$$pIPESE
000188160 909C0 $$pLENI$$xU10315$$0252044 000188160 909C0$$xU11808$$0252296$$pCEN
000188160 909CO $$qGLOBAL_SET$$pconf$$pSTI$$ooai:infoscience.tind.io:188160
000188160 917Z8 $$x167324 000188160 937__$$aEPFL-CONF-188160
000188160 973__ $$rREVIEWED$$sPUBLISHED$$aEPFL 000188160 980__$$aCONF