| Sažetak | Hlađenju robe u supermarketima predaje se velika pažnja danas. Velika pažnja predaje se jednim dijelom radi zadržavanja kvalitete proizvoda i dužeg očuvanja, što daje prednost pred konkurencijom, a drugim dijelom radi potrošnje energije potrebne za hlađenje. Gledajući iz perspektive potrošnje energije potrebne za hlađenje, Uredbom br. 517/2014, Europskog parlamenta i Vijeća, o fluoriranim stakleničkim plinovima (tzv. F-gas regulativa), današnja se istraživanja u rashladnoj, klimatizacijskoj tehnici i dizalicama topline, sve više usmjeravaju na primjenu prirodnih radnih tvari kao što su amonijak, ugljikov dioksid i ugljikovodici. Radne tvari, osim što ne smiju imati utjecaj na razgradnju ozona (engl. Ozone Depletion Potential, ODP jednak vrijednosti 0), trebaju imati što manji potencijal globalnog zagrijavanja (engl. Global Warming Potential, skraćenica GWP). Navedena Uredba na taj način promovira primjenu održivih tehnologija i održivih prirodnih radnih tvari u rashladnim sustavima.
U ovom diplomskom radu primarno je, kroz četiri točke rada, prikazan proces projektiranja transkritičnog rashladnog sustava s ugljikovim dioksidom (CO2) kao radnom tvari za potrebe skladištenja robe u supermarketu. Ukupni rashladni učinak plus temperaturnog režima hlađenja iznosi 42,41 kW, dok ukupni rashladni učinak minus temperaturnog režima hlađenja iznosi 11,4 kW. Odabrani supermarket sadrži samoposlužni prostor površine 700 m2 i nalazi se u sjeverozapadnom dijelu Hrvatske.
U prvoj točci rada prikazan je termodinamički proračun za određivanje ukupnih rashladnih opterećenja dviju rashladnih komora i dviju rashladnih vitrina koje se nalaze u prostoru supermarketa. Analogno prikazanim termodinamičkim proračunima proračunavaju se i sve preostale rashladne komore i rashladne vitrine. Rezultati termodinamičkog proračuna rashladnih komora daju ukupno rashladno opterećenje plus rashladnih komora 10,82 kW, dok je rashladno opterećenje minus rashladnih komora 5,16 kW. Isto tako, rezultati termodinamičkog proračuna rashladnih vitrina daju ukupno rashladno opterećenje plus rashladnih vitrina 31,59 kW, dok je rashladno opterećenje minus rashladnih vitrina 6,24 kW. Nadalje, kroz drugu i treću točku rada, odabran je rashladni proces, definirane su karakteristične točke sustava te su dimenzionirane glavne komponente rashladnog sustava (kompresorski multisetovi, prigušni ventili, isparivači i hladnjak plina). Rashladni sustav sastoji se od 2 multikompresorska seta, hladnjaka plina, 5 rashladnih komora i 21 rashladne vitrine.
Budući je rashladni sustav projektiran na način da sadrži opciju iskorištavanja otpadne topline, u četvrtoj točci rada, prikazana je analiza energetskih ušteda tijekom eksploatacije supermarketa na račun korištenja otpadne topline za grijanje prostorija supermarketa i zadovoljavanje potreba za potrošnom toplom vodom. Sustav grijanja je projektiran za ogrjevni učinak od 47 kW temperaturnog režima 27 ⁰C/40 ⁰C, dok je sustav potrošne tople vode projektiran za ogrjevni učinak od 8 kW temperaturnog režima 45 ⁰C/65 ⁰C.
Kako je u prvoj točci rada termodinamički proračunato ukupno rashladno opterećenje odabrane otvorene rashladne vitrine, u petoj točci rada, prikazana je analiza ugradnje staklenih vrata na odabranu otvorenu rashladnu vitrinu. Ugradnja staklenih vrata i bočnih, staklenih ploha od dvostrukog stakla na otvorenu rashladnu vitrinu, rezultira smanjenjem ukupnog rashladnog opterećenja od 52 %. Nadalje, provedena je usporedba potrošnje električne energije otvorene i zatvorene rashladne vitrine, a koja pokazuje da je otvorenoj rashladnoj vitrini dnevno potrebno 27,08 kWh/dan, dok je zatvorenoj rashladnoj vitrini potrebno 19,16 kWh/dan.
Na samom kraju rada, koji ujedno pokriva i posljednju, šestu točku rada, nalaze se funkcionalne sheme kompletnog rashladnog sustava i automatske regulacije. Nadalje, prilog diplomskog rada sadrži spomenute funkcionalne sheme na crtežima: tlocrta supermarketa i razmještaja rashladne opreme, razmještaja isparivača u supermarketu i sheme strojarnice rashladnog sustava. Isto tako, u prilogu su priloženi rezultati termodinamičkog proračuna određivanja ukupnih rashladnih opterećenja rashladnih komora. |
| Sažetak (engleski) | Today, great attention is paid to the cooling of goods in supermarkets. First, great attention is paid in part to maintaining product quality and longer preservation, which gives an advantage over the competition, and secondly to the consumption of energy required for cooling. Seen from the perspective of energy consumption required for cooling, Regulation no. 517/2014, of the European Parliament and the Council, on fluorinated greenhouse gases (so called F-gas regulation), and with today’s research in refrigeration systems, air conditioning systems and heat pumps, are increasingly focused on the use of natural refrigerants such as ammonia, carbon dioxide and hydrocarbons. In addition to not influencing ozone depletion (ODP equal to 0), the refrigerants should have the lowest possible global warming potential (GWP). This Regulation thus promotes the application of sustainable technologies and sustainable natural substances in refrigeration systems.
In this paper, primarily through four points of paper, the process of designing a transcritical CO2 refrigeration system for supermarket application is presented. The total cooling load of medium temperature regime is 42,41 kW, while the total cooling load of low temperature regime is 11,4 kW. The selected supermarket contains a self-service area of 700 m2 and is located in the northwestern part of Croatia.
The first point of the paper presents a thermodynamic calculation for determining the total refrigeration loads of two refrigeration chambers and two refrigeration cabinets located in the supermarket space. All remaining refrigeration chambers and refrigerated cabinets are calculated analogously to the thermodynamic calculations shown. The result of the thermodynamic calculation for the total cooling load of medium temperature chambers is equal to 10,82 kW, while the total cooling load of low temperature chambers is equal to 5,16 kW. Also, the result of the thermodynamic calcualtion of refrigerated display cases show that the total cooling load for medium refrigerated cabinets is equal to 31,59 kW, while the total cooling load for low temperature refrigerated cabinets is equal to 6,24 kW. Furthermore, through the second and third operating points, the refrigeration process was selected, the characteristic points of the system were defined, and the main components of the refrigeration system (compressor multisets, valves, evaporators, and gas cooler) were dimensioned. The refrigeration system consists of 2 multicompressor sets, gas cooler, 5 refrigeration chambers and 21 refrigerated display cases.
Because the cooling system is designed to contain the option of heath recovery, in the fourth point of the paper, an analysis of energy savings during the operation of the supermarket at the expense of using waste heat to heat supermarket premises and meet domestic hot water needs. The heating system is designed for a heating output of 47 kW with a temperature regime of 27 ⁰C/40 ⁰C, while the domestic hot water system is designed for a heating output of 8 kW with a temperature regime of 45 ⁰C/65 ⁰C.
As the total refrigeration load of the selected open refrigerated display case was thermodynamically calculated in the first operating point, in the fifth operating point, the analysis of the installation of glass doors on the selected open refrigerated display case is presented. Installing glass doors and side, double-glazed glass panels on an open refrigerated display case results in a 52% reduction in total refrigeration load. Furthermore, a comparison of electricity consumption between open and closed refrigerated display cases was performed, which shows that an open refrigerated display case requires 27,08 kWh/day, while a closed refrigerated display case requires 19,16 kWh/day.
At the very end of the paper, which also covers the last, sixth point of paper, there are functional diagrams of the complete cooling system and automatic regulation. Furthermore, the addition of the paper contains the mentioned functional diagrams on the drawings: floor plan of the supermarket and arrangement of refrigeration equipment, arrangement of evaporators in the supermarket and diagram of the cooling system machine room. Also, the results of the thermodynamic calculation of the total cooling loads of the cooling chambers are attached. |
