Question

(+30) You have a half-filled hot tub that is cold (T-25 "C). You have two ways of heating it up: add more hot water (maximum T = 45 "C) and/or turn on the electric heater (5 kW). The total water capacity of your well-insulated hot tub is 1.0 m3, and the desired water temperature is 38"c. a. If you just use the electric heating element to heat up the existing water, without adding any new hot water: i. (+8) How much electric energy is needed, in k ii. (+3) How long would it take to get the water to temperature, in minutes? b. If you just add new hot water, without using the electric heating element i. (+2) How long does it take to fill the tub if the water flows at a rate of 0.01 m'/min? i. (+8) What is the new temperature of the water in the hot tub? ili. (+5) How much electric energy is needed, in kl, to bring it to the desired temperature? (+2) Which method is faster? (+2) Which method is likely more efficient? Why? c. d. IF

Answer 1

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