Studien syftar till att undersöka teorin bakom kortslutningskåpan, dess potential och begränsningar. Undersökningen inleds med en litteraturstudie vilken följs av en fallstudie där ett system med kortslutningskåpa, med avseende på energibehov och systemkostnad, jämförs med ett system med en vanlig kåpa respektive ett system med värmeåtervinning. Litteraturstudien visar att kortslutningskåpan kan minska nettoluftflödet från köket och på så sätt minska uppvärmningsbehovet. Introduceras för stor mängd kortslutningsluft läcker värme och föroreningar från kåpan till köket. Maximalt kunde 21% av det totala frånluftsflödet kortslutas utan läckage. Fallstudiens energiberäkningar har utförts i programmet BELOK Värmeåtervinning samt i ett av författaren kodat program. De tre systemen testades för två fall med olika drifttid, en lunchrestaurang med låg drifttid och en hamburgerrestaurang med hög drifttid. Kortslutningskåpan minskade energibehovet med 15 % och det återvinnande systemet med dryga 80 %. Trots det minskade energibehovet var det värmeåtervinnande systemet inte ekonomiskt lönsamt i lunchrestaurangen, ty drifttiden var för låg för att de höga investeringskostnaderna skulle hinna betala sig. Kortslutningskåpan betalade sig dock efter 4,2 år. I hamburgerrestaurangen, där drifttiden var högre, betalade sig kortslutningskåpan efter 1,3 år och det återvinnande systemet efter 3,2 år. Över 15 år var dock det återvinnande systemet betydligt mer lönsamt. Jämfört med en vanlig kåpa minskade kortslutningskåpan kostnaderna med 13,3 %. Över samma tidsperiod minskade det värmeåtervinnande systemet kostnaderna med 39,5 %. / This study aims to investigate the theory behind the short circuit hood, its potential and limitations. This is done partly as a literature study and partly as a case study where a system with a short circuit hood, in regards of energy demand and system cost, is compared with a system using an exhaust only hood and with a system using heat recovery. The literature study shows that the short circuit hood can reduce the net air flow from the kitchen and thus decrease the heating demand. If too much air is short circuited, heat and contaminations will leak from the hood to the kitchen. A maximum of 21 % of the total exhaust flow could be short circuited without leakage. The energy calculations in the case study were performed using the program BELOK Värmeåtervinning and in a program coded by the author. The three systems were tested for two cases with different operating hours, a lunch restaurant with few operating hours and a hamburger restaurant with many hours. The energy demand was reduced by 15 % using a short circuit hood and by more than 80 % using the heat recovery system. Despite the reduced energy demand, the heat recovery system was not economically profitable in the lunch restaurant, the operating hours were too low for the big investment costs to pay off. However, the short circuit hood payed off after 4,2 years. In the hamburger restaurant where the operating hours was higher, the short circuit hood payed off after 1,3 years and the heat recovery system after 3,2 years. Over 15 years, however, the heat recovery system was significantly more profitable. Compared to an exhaust only system the short circuit hood reduced the costs by 13,3 %. Over the same period, the heat recovery system reduced the costs by 39,5 %.

This project was performed to evaluate if waste heat from hotel kitchens is enough to heat outdoor swimming pools in southern Europe or if it can be used as a compliment to another heat source. Another aim was to analyze the simulations and calculations of the pools and the heat recovery system. Then estimate how much annual costs would be reduced when using the exhaust air in the heat recovery system, in comparison with the original heating system. If the project showed positive results the purpose was to select a waste heat recovery system that can integrate with Ozonetech’s ozone generator, keep a high temperature in the pool and reduce emissions of greenhouse gas by using waste heat. Ozonetech would also conduct a pilot study in Stockholm and eventually develop their own product. A simulation model of three different outdoor pool sizes were conducted. The models were constructed and meshed in COMSOL Multiphysics. Average weather conditions for Malaga, Spain, were implemented in the model. The models were simulated by integrating each physical phenomenon in COMSOL, by using the Multiphysics interface. This created convection, emitted radiation and evaporation as thermal heat losses from the pool models. The pools were simulated to determine heating demand, heating period and required inlet temperature to make up for thermal heat losses. A mathematical model of the thermal heat losses and gains were conducted to easily receive a result for the heat demand each month of the year. A mathematical model of the possible heat recovery from hotel kitchens were performed to determine heat recovery for various kitchen sizes. By knowing the heat demand and possible heat recovery from different kitchens, a heat exchanger was selected. The heat exchanger was selected based on literature review, requirements and discussions with manufacturers. A life cycle cost analysis and calculated payback time compared original heating systems with new heat recovery system. A sensitivity analysis using Gauss error propagation concluded the project. The simulations showed that all investigated outdoor pools require additional heat during the night, due to extensive heating periods. Since the kitchen is only active during the day, the pool requires an additional heat source during the night. This conclude that the new heat exchanger only can replace the original heating system during the day. The mathematical model of the heat transfer from the kitchen determined that the maximum heat capacity approximately is 350 kW ± 10.5 kW. The waste heat can only be used to heat small and medium sized pools, since the heat loss is too great for a large pool. Selected air to water heat exchanger that meets the requirements is an air cooler with finned tubes from Alfa Laval. The fins and the coil should be treated to form an e-coat. After calculating the life cycle cost it was determined not profitable to replace a heat pump for a small pool, since the life cycle cost was greater for the new heating system. However, it is profitable to replace an electric heater with the new heat exchanger together with three of the smallest ozone generators during the day, for a small pool. Costs will be reduced by 44 600 – 202 000 kr ± 5%. Payback time will be 2.4 – 3.2 years ± 9%. It is also profitable to replace a water to water heat exchanger heated with either electricity or oil, during the day, with the new heat exchanger combined with either of the ozone generators for a small pool. Costs will be reduced by 310 000 – 698 000 kr ± 5%. Payback time will be 1.8 – 2.5 years ± 9%. It is profitable to replace all original heating systems during the day with the new heat exchanger combined with either of the ozone generators for medium sized pools. Costs will be reduced by 689 000 – 12 600 000 kr ± 5%. Payback time will be 2.2 – 22 months ± 7%.