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TECHNOLOGYHeat Transfer CalculationThe heat transfer was calculated for bowls and plates before they were designed. Because The heat transfer was calculated for bowls and plates before they were designed. Because the PCM heat storing capacity should be enough for keeping foods warm during service, on the other hand, the heat transfer from PCM to outside environment of dishwares should not be over the limit. And the heat capacity of PCM is 2,1 kJ/(kg.K)(1,91 BTU/(kg.K)) , when we calculated the heat capacity of PCM which in bowls and plates, we optimized the volume and capacity with calculations. According to service time of meals (20-30 min), the heat transfer values are under the limit.

Thermal Conductivity CoefficientsThermal Conductivity CoefficientsKbone china: 80 W /( m-K )Ksilicon rubber: 1,25 W /( m-K )

Bowl A: 0,00636 m2d: 0,002 mPCM volume: 63,6 cm3PCM weight: 0,053424 kg ; PCM Heat Capacity: 0,126 kJ/(kg.K) PCM weight: 0,053424 kg ; PCM Heat Capacity: 0,126 kJ/(kg.K) Q/tbone china=3816 watts =13020 BTU/hour, Q/tsilicon = 85,4 watts = 290 BTU/hour

For the bowl which will be used for soups and porriges, it will be easier to keep the food at the right and safe temperatures because of full contact with the bowl.

Within the plate, PCM volume will be 226,87 cm3 and surface area will be 226,87 cm2. As we have more surface area compaired to the bowl and as it is known that heat exchange depends on the surface area, it is easy to keep heat in main meal.depends on the surface area, it is easy to keep heat in main meal.

Heating the PCMTo give the PCM the first heat, we found a good way without introducing any new electrical devices into the process – the dishwasher.According to the manufacturer PCM gel can store the heat for 2 hours. The phase state of the PCM gel pack should be in liquid phase before the using. The idea is to re-charge at PCM in the dishwasher at approx 90 to 95 C degrees.

According to market research, generally high temperature conveyor dishwashers are used According to market research, generally high temperature conveyor dishwashers are used in the hospitals kitchen. The washing cycle is hygienic, which means that the last wash is at a temperature of 95 degrees, which reduces the number of germs even more than the normal wash cycle. Depending on the wash cycle, it may vary from 55 min to 2 hours. The temperature is changing between 70 C and 95 C. The time to recharge the inner PC M to preferred temperature is enough.

The dishwares should be used after washing in 60-70 min and they should be stored as The dishwares should be used after washing in 60-70 min and they should be stored as normal plates – stacked on top of each other. In this way there will be an air gap between silicon rubber and bone china part, so the heat will be kept for longer time.

For cold food distribution the type of PCM is different, suitable for cold temperatures. All the properties of material and design are the same. To recharge the industrial refrigerators will be used in hospital kitchen to keep the PCM temperature at minimum degrees as possible. To recharge the cold PCM they will be kept in the refrigerator for 30 minutes before using according to producer.according to producer.

PlateA: 0,0226 m2d: 0,004 mPCM volume: 226 cm3 ; PCM Heat Capacity: 0,4746 kJ/(kg.K) PCM weight: 0,18984 kgQ/tbone china= 13560 watts =46268 BTU/hourQ/tbone china= 13560 watts =46268 BTU/hourQ/tsilicon = 303,68 watts = 1033,87 BTU/hour

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TECHNICAL DRAWINGS

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TECHNICAL DRAWINGS

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ACKNOWLEDGEMENTS

THANK YOU FOR THE CONTRUBITION!

AND

Regionaalhaigla Staff

Martin PärnHead of D&E Departmentof TUT and EAA

Janno Nõu Industrial Designer

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