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COST OF OPENING A DOOR

COST-OF-OPENING-A-DOOR

Cost of Opening a Door =7 

 

Energy Calculation

 

E = m C ∆T

m : Mass of Air

C : Specific heat of Air at given Temperature

∆T : Temperature Difference

 

m = Density X Volume

Density of Air at 40˚C = 1.127 Kg/cu. meter

C = Specific Heat = 1.005 KJ / (Kg ˚C)

∆T = Temperature Difference = 15˚C

(assuming outside temperature is 40˚C and inside is 25˚C)

 

Volume = Area X Velocity of Air from Door X Time of Opening

(Say :       Door Size = 8ft X 4 ft

                Velocity = 1 m/s = 200 fpm

                Time of Opening = 1 min

                Volume = 32 X 200 X 1 = 6400 cu. ft. = 181.22 cu. meter)

 

m = Density X Volume

(from Above             = 1.127 Kg/cu. meter X 181.22 cu. meter

                                = 204 Kgs)

 

E = m C ∆T

= 204 kgs X 1.005 KJ / (Kg ˚C) X 15˚C

= 3075.3 KJ = 0.85425 KWh

Thus –

India if Per KWH cost of Power is Rs 8.10

Cost of Opening the Door of Size 8ft X 4ft for 1 min is = Rs 6.92

Cost of Running an Air Curtain of 4 ft = 400W (Input Power) for 1 minute = 6 paise

Rate per Kwh X Time X Power Input

8.10 X 1/60 X 0.4 = 5.4 paisa

 

Net Saving = Rs 6.92 – 0.06 = Rs 6.86

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