Consider a refrigerator that consumes 400 W of electric power when it is running. If the refrigerator runs only one quarter of the time and the unit cost of electricity is P10.50/kWh, the electricity cost of this refrigerator per month (30 days) is
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Consider a refrigerator that consumes 400 W of electric power when it is running. If the refrigerator runs only one quarter of the time and the unit cost of electricity is P10.50/kWh, the electricity cost of this refrigerator per month (30 days) is
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- A refrigerator has a broken light bulb inside that is constantly turned on even when the refrigerator door is closed. If the light bulb uses 20 W of power and the refrigerator has a COP of 1.4, what would be the total cost of power consumption of the entire refrigerator? Assume electricity costs P12 per kWh and the refrigerator is opened an average of 15 times per day for 30 seconds.By supplying energy to a house at a rate of 25,000 kJ/hr, a heat pump maintains the temperature of the dwelling at 20 C when the outside air is at -10 C. If electricity costs 8 cents per kW-hr, determine the minimum theoretical operating cost to heat the house for 24 hours. $1.97 O $1.37 $1.75 O $1.51 O$1.64A heat pump with a COP of 3.2 is used to heat a perfectly sealed house (no air leaks). The entire mass within the house (air, furniture, etc.) is equivalent to 1200 kg of air. When running, the heat pump consumes electric power at a rate of 5 kW. The temperature of the house was 7°C when the heat pump was turned on. If heat transfer through the envelope of the house (walls, roof, etc.) is negligible, the length of time the heat pump must run to raise the temperature of the entire contents of the house to 22°C is (a) 13.5 min (b) 43.1 min (c) 138 min (d) 18.8 min (e) 808 min
- A Carnot heat pump is used to maintain the temperature inside a building at 20 ∘C. Significantly, the colder it gets outside, the more heat is lost through the walls and windows of the building. Assume that 45 kW of heat are lost for each degree difference between the outside and the inside temperature. That means that the colder it gets, the harder the heat pump will need to work. However, for safety reasons, the controller circuit for the heat pump limits its electrical power consumption to 195 kW. What's the coldest it can get outside before the heat pump can't maintain the building temperature adequately?A heat pump keeps the house at 20°C while the ambient (outside) temperature is 0°C. from the roof and The heat loss from the walls is 3000 kJ/h per degree temperature difference between the indoor and outdoor environment. Determine the minimum theoretical power in kW required to operate the heat pump.A device collects energy from the sun's rays and produces a high temperature of 95 °C. A small heat engine then uses this as a high temperature reservoir and operates at an ambient temperature of 15 °C. What is the maximum possible thermal efficiency of this heat engine? After some improvements are made to the solar energy collector, the high temperature it produces is now Tnew. If it is given that the new maximum possible thermal efficiency of the heat engine is double the previous one, what is Tnew? (Assume that the ambient temperature stays the same)
- An inventor claims to have a solar powered heat pump that receives energy as heat from the sun at the rate of 10 kW and extracts energy as heat from the environment at the rate of 7 kW. This system does not require any shaft or electrical power input. If you think this device is impossible, explain why using basic principles to support your argument. If you think it might be possible, what would be the steady-state rate of transfer of energy as heat to the house? (Assume TH = 20 Cand TL = -15 C).A household refrigerator with a COP of 1.25 removes heat from the refrigerated space at a rate of 90kJ/min Determine (a) the electric power consumed by the refrigerator and (b) the rate of heat transfer to the kitchen air.A cooling machine operates in an environment with a temperature of 23 ° C and gives 210 kJ of heat per minute to this environment. The performance coefficient of the refrigerator is 4.5. Find the required power (in kW) to operate this cooling machine and the lowest temperature inside the cooling machine.