"A risk assessment of the Piql Services" by FFI

Heat capacity

The heat capacity of the room consists of the heat capacity of the air in the room, and the heat capacity of equipment in the room and the room walls.

The volume of the room is 640 m 3 . At a temperature of 20° Celsius, the air mass would be 760 kg. The specific heat capacity of air at constant pressure is very close to 1kJ/kg/K (1K = 1 degree C), so the total heat capacity of the air in the room is 760 kJ/K. There is no specific information on other equipment. However, the stored items seem to be composed of polymer bins, possibly on aluminium shelves. Supposing that the total mass load on the floor is 1000 kg/m 2 , and half the room is filled up with this, the total mass inside the room would be 43000 kg. The heat capacity of aluminium is 0,9 kJ/kg/K, and polyethylene is 1,5 kJ/ kg/K. This would make the total heat capacity of the equipment inside to 52000 kJ/K (supposing half and half aluminium and polyethylene). In addition, the walls have a heat capacity, but given the large uncertainties, this is not taken into account.

Calculation of temperature rise

Given the lack of information of the items in the room, the temperature rise of the empty room is first calculated, with only the robots working inside, and no energy loss to the outside.

Empty room

Heat capacity 760 kJ/K

Energy input 1400 W: dT/t=1400/760000 = 0,0018 K/s = 6,6 K/hour

Energy input 300 W: dT/t=300/760000 = 0,0004 K/s = 1,4 K/hour

Room with 43 tons equipment

Heat capacity 52760 kJ/K

Energy input 1400 W: dT/t=1400/52760000 = 0,000027 K/s = 0,096 K/hour

Energy input 300 W: dT/t=300/52760000 = 0,0000057 K/s = 0,02 K/hour

Energy loss

The above calculations do not take into account loss of energy from the room, but suppose that the room is thermally insulated from the surroundings. This is obviously not the case. Thermal energy will be exchanged with the surroundings by conduction through walls, ceiling and floor, and by exchange of air, even if the ventilation system is not working. Which way the energy

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FFI-RAPPORT 16/00707