Physics, 12.02.2020 05:51 anaclaramigli

26 people is to be airconditioned. A person in the classroom typically dissipates heat at a rate of 360 kJ/h. The room is lit with 15 light bulbs which each consume 40 W. A 200 W fan also operates in the room near a door to a computer closet. This fan pulls warm air into the classroom under the door at a rate of 200 kg/h. The room gains 10 kJ in energy (enthalpy) for each kg of warm air which enters. The air comes under the door at 10 m/s and leaves the room with negligible velocity through a large vent 3 m above the floor. Otherwise the room is well sealed. Finally, the room gains 5,000 kJ/h by heat transfer through the walls and windows. Determine the air-conditione.

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Answer from: potato3999

The capacity of refrigeration =5.35kw

Explanation:

Total people in classroom =26

One person dissipates =360kj/h

So 26 person will dissipates =360 × 26

=2.6kw

15 light bulb with 40w each

Total heat dissipates 15×40 =600

=0.6kw

Fan will dissipate =200w

=0.2kw

Room gain air at a rate of =200kg/h

Warm air enthalpy =10kj/kg

Total heat coming with warm air = 200×10

0.555kw

Heat coming from window walls =5000kj/h

=5000/3600= 1.388kw

Total heat coming in the room =2.6+0.6+0.2+0.55+1.388

=5.35kw

To maintain room at steady temperature

Heat should be removed at constant rate

Energy balance =energy in/energy out

Capacity of refrigeration =5.35kw

Answer from: Quest

All these statements are related to drake's equation. it is a probabilistic equation that shows an aproximate number of civilizations in our galaxy that we can communicate with. all the numbers that are inserted into equation are not precisely known so the result varies from 1000 to 100,000,000. the equations was not created to calculate exact number of extraterrestrial civilizations but to increase scientific knowledge how to find them.the equation is: $n= r_{*} *f_{p}*n_{e}*f_{l}*f_{i}*f_{c}*l$ where: n= represents the number of civilizations in our galaxy that we could in principle communicate with today. $r_{*} =$ the average rate of star formation in our galaxy $f_{p} =$ the fraction of those stars that have planets $n_{e} =$ represents the number of planets in the galaxy that are in principle capable of having surface liquid water and life. $f_{l} =$ essentially represents the probability that life eventually arises on a habitable planet. represents the number of life-bearing planets in the galaxy. $f_{i} =$ epresents the total number of planets on which intelligent beings have evolved and developed a communicating civilization at some time in the galaxy's history. $f_{c} =$ essentially represents the probability that on a planet with life, some organisms will eventually evolve to the point where they can build radio telescopes. $l =$ is a factor that depends on how long civilizations that reach our level of technology are able to survive.

Answer from: Quest

Ithinks its b hope that

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