Beta 1


Title Dimensionering og implementering af varmepumper i forbindelse med udtørringsanlaeg ved varierende drift
Author Lindhard, Troels
Foged, Esben Vendelbo
Supervisor Elmegaard, Brian (Termiske Energisystemer, Institut for Mekanisk Teknologi, Danmarks Tekniske Universitet, DTU, DK-2800 Kgs. Lyngby, Denmark)
Institution Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
Thesis level Master's thesis
Year 2011
Abstract At benytte varmepumper til varmegenvinding har i de senere år fået stor opmærksomhed i industrien. Der er stor efterspørgsel på teknologien i mange brancher, og potentialet er stort. I denne kandidatafhandling undersøges potentialet ved at benytte varmepumper til varmegenvinding i forbindelse med HVAC-anlæg (Heating, Ventilation and Air Conditioning) til udtørring. Udtørringsenheden fungerer ved, at friskluft og recirkuleret luft fra bygningen blandes, hvorefter en køleflade køler luften, således at vandet indeholdt i luften udkondenserer. Herefter genopvarmes luften over en varmeflade til en passende temperatur, hvorefter den blæses ind i bygningen igen ved en lavere luftfugtighed. Der er således mulighed for at benytte varmen optaget i kølefladen til genopvarming i varme fladen ved brug af en varmepumpe. Afhandlingen tager udgangspunkt i et konkret udtørringsanlæg i opskæringsafsnittet ved Danish Crowns slagteri i Horsens. Først bliver teorien omkring komponenterne i systemet gennemgået, hvorefter en model over udtørringsenheden med integreret varmepumpe opstilles. Modellen benyttes til at simulere driften igennem et år på timebasis og resultaterne analyseres, ved brug af termodynamisk og økonomisk teori samt exergianalyse. Resultaterne fra den første simulering indikerer, at systemet ikke fungerer optimalt, og en exergie flektivitetsanalyse af komponenterne bekræfter dette. Det blev endvidere observeret, at kompressoren i alle timer af året arbejder udenfor sit arbejdsområde. Fordamper- og kondensatorstørrelsen optimeres derfor således, at dette ikke er tilfældet. Ud fra grænserne for kompressoren bliver der lavet en termoøkonomisk optimering, således at varmepumpesystemet får så lav en tilbagebetalingstid som muligt. Modellen bliver herefter simuleret igen, med de nye varmevekslerstørrelser og tilbagebetalingstider samt exergieffektiviteter bliver fundet for den den optimerede model. Analysen viser, at tilbagebetalingstiden er blevet reduceret med ca. 30%, og kompressor exergieffektiviteten er blevet forget med 100 %. Afslutningsvis foretages der en analyse af hvorledes valget af kompressor, og dermed kapaciteten for varmepumpen, gøres bedst muligt under hensyntagen til dellastvirkningsgrader for kompressoren. Denne analyse viser, at det bedst kan betale sig at opbygge systemet med to kompressorer - en lille og en stor kompressor - da denne konfiguration giver den laveste tilbagebetalingstid, som er ca. 2 ar.
Abstract The usage of heat pumps in the industry for heat recovery has gained great attention during the last couple of years. Due to this, there is a large demand for this technology within many businesses and the potential is large. In this Master's Thesis will examine the potential of using a heat pump for heat recovery within a HVAC drying unit. The HVAC-unit works by rst mixing air from outside the building with re-circulated air from inside the building. The mixed air is passed by a cooling surface and thereby some of the moisture in the air is condensed and the humidity reduced. Afterwards, the air is reheated by heating surface to an appropriate temperature and lead back into the building with a reduced humidity. There is a great potential for using the heat absorbed in the cooling surface for reheating the air at the heating surface using a heat pump. The thesis is based on an air drying unit in the cutting section at the Danish Crown slaughterhouse in Horsens. First the theoretical background for the components used in the system will be introduced, and afterwards the air drying unit with integrated heat pump is modelled for simulation purposes. The model is used for simulating a year of operation on an hourly basis. The results are then analysed using thermodynamic, thermoeconomic and exergy theory. The results from the first simulation indicate that the system is not functioning at its optimum, and an exergy analysis for the different components confirms this. It was also observed that the compressor worked outside its operational range every hour of the year. The size of the evaporator and condenser is therefore optimised so this can be avoided. A thermoeconomic optimization is made based on the boundaries of the operational range of the compressor, with the focus of minimizing the simple payback time. Afterwards a new full-year simulation is conducted with the optimised heat exchanger sizes, and the simple payback times and exergetic efficiencies are found for the optimised model. The analysis shows that the simple payback time is reduced by 30% and the exergetic efficiency for the compressor is increased 100%. Finally, an analysis is conducted of how the choose compressor, and thereby the capacity of the heat pump. This analysis takes the part load eciencies of the compressor into consideration. This analysis shows that from an economical point of view the best solution is to use two compressors - one small and one large. This ensures the best part load eciencies and reduces the pay back time to around 2 years.
Note Afhandlingen er fortrolig
Note The thesis is confidential
Imprint DTU Mekanik
Pages 234
Series MEK-TES-EP-2011-10
Admin Creation date: 2011-12-13    Update date: 2011-12-14    Source: dtu    ID: 314385    Original MXD