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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10990/745

Autori: Menegon, Diego
Supervisore afferente all'Università: CORTELLA, GIOVANNI
Supervisore non afferente all'Università: FEDRIZZI, ROBERTO
Titolo: Development of a Dynamic Test Procedure for the Laboratory Characterization of HVAC systems
Abstract (in inglese): The heating and cooling demand requires about the 40 % of the energy consumptions. This demand is mainly satisfied by means of electricity or fossil fuels driven systems. The alternative is the implementation of renewable sources, whose large market potential has still not been fully reached due to high investment costs, lack of knowledge of designers and installers, lack of reliability, lack of test procedures to characterize systems’ performance before marketing. Hybrid systems implement different energy sources into one system. The interaction of different components, the complex layout required for the implementation of different sources, the working principle of components (continuous or discontinuous modes) and the control strategy affect the performance of those systems. The characterization of system performance is not trivial on account of the influence of those numerous factors. Different standards are available to test single components (chillers or heat pumps) or solar systems but not all the available technologies are covered (i.e. adsorption chillers driven). Most of them foresee only stationary characterization disregarding the effects of dynamic working conditions. The performance evaluation under stationary conditions is not sufficient to perform a reliable evaluation of performance. The work of this thesis regards the development of a dynamic test procedure for the laboratory characterization of heating and cooling systems. The activity is divided into two mains parts. The first one regards the development and application of the procedure at component level while in the second one the procedure was further developed for the application at system level. In the procedure developed at component level, the seasonal boundary conditions of the tested component are defined considering its interaction with the system by means of a numerical simulation. From the seasonal boundary conditions, a short sequence is defined by classifying the working conditions and selecting a representative part. From the test results of the sequence, the seasonal performances are extrapolated. Numerous tests have been carried out in order to validate the procedure, according to several criteria. The tests were performed on an adsorption chiller (SorTech ACS 08) and on an electrically driven heat pump (Clivet WSHN-EE 31). The performances evaluated with a short sequence deviate from the seasonal ones about 2 % and the dynamic tests highlight the behaviour of those components under dynamic conditions. Furthermore, the results have been compared with those obtained by two other available test methods. The first is the bin method (EN 14825) that uses stationary tests of the chiller at full and part-load to evaluate its seasonal performance. The second is the Component Testing – System Simulation method that requires a numerical model validated by stationary test; the seasonal performances are evaluated by means of a component simulation. The deviation of developed method with the two mentioned procedures are calculated. For the adsorption chiller, the dynamic test estimates performances 15 % lower than the two methods while for the heat pump the deviation depends from the working mode. In heating mode, the deviation is about 5 % while in cooling is about 29% since the machine is controlled with numerous starts and stops; in this second case the effect of transients becomes important. The whole system test procedure has been developed with the objective to be at the same time easily implemented, cost attractive for industries and reliable. The adaption of the procedure at system level does not require any more simulations of the system to define the boundary conditions, which are taken directly from the wheatear file simplifying this phase. However, not all the components of the system are installed in the test facility and therefore emulation models are needed. The emulation is performed without commercial software. The selection of a short sequence is performed classifying the days using clustering analysis. The procedure is applied to a hybrid system (a solar assisted heat pump system) considering four European climates (Bolzano, Zurich, Gdansk and Rome). The seasonal performance figures are extrapolated from the test results and compared with the annual simulation of the system. In all the test cases, the seasonal performance factors are lower than the simulated one up to about 20 % (only one case is 20 %, the others are up to 10 %). The simulation disregards some transient behaviours that are visible during the test. Moreover, the test allows to highlight some limits of the tested system such as the control of storage charge, inefficient use of solar energy for the space heating and control of heat pump. The advantage of the dynamic test is that the test outcome also gives advice for the improvement of the system layout and or control. At the “Institute for Solar Energy SPF” of the “University of Applied Science of Rapperswil HSR” in Switzerland, a six-day sequence has been developed to perform a direct evaluation of performance in order to reduce the cost of test (from a twelve-days to a six-days test). The sequence has been developed and optimized for a reference solar assisted heat pump system. About one hundred different systems were simulated to verify the representativeness of sequence for different system configurations. The deviation of performance figures extrapolated directly from test (with a 365/6 multiplication factor) and the annual simulation are used as indicators of the representativeness of the six-day sequence. Some independent parameters lead to a predictable deviation in the performance evaluation that can be greatly reduced by simple correction factors. These parameters can be reduced to the nominal collector field power and to storage losses. The deviation is reduced to a maximum value of 5 % and a standard deviation of 21.5 % for the different systems studied. The sequence developed at the SPF-HSR is compared to the sequence defined with the methodology presented in this thesis. The deviation of the total seasonal performance factor evaluated with the two methods is about 1 %.
Parole chiave: Laboratory Test; Dynamic Test; Whole system testing; Component testing; Heating and cooling systems; Renewable energy; Solar assisted heat pump system; Heat pumps
MIUR : Settore ING-IND/10 - Fisica Tecnica Industriale
Lingua: eng
Data: 15-apr-2016
Corso di dottorato: Dottorato di Scienze dell'ingegneria energetica e ambientale
Ciclo di dottorato: 28
Università di conseguimento titolo: Università degli Studi di Udine
Luogo di discussione: Udine
Altre informazioni: Struttura di co-aggregazione: EURAC/European Academy. Istituto per le energie rinnovabili di Bolzano
Citazione: Menegon, D. Development of a Dynamic Test Procedure for the Laboratory Characterization of HVAC systems. (Doctoral Thesis, Università degli Studi di Udine, 2016).
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