Chemical Engineering - Heat Transfer - Discussion
Discussion Forum : Heat Transfer - Section 1 (Q.No. 15)
15.
In Joule's experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglecting the heat capacity of agitator, the temperature of water (in °C) is
Discussion:
22 comments Page 1 of 3.
Muhammed Ishak T N said:
3 years ago
@All.
Guys please try to solve this. The correct value for cp is 4180
By 1st law of thermodynamics;
Energy neither be created nor destroyed, it can be transformed from one form to another form.
So,
For 500 turns.
mgh = mcp( T2 - T1),
500*40*9.8*4 = 20*4180( T2-25),
By solving these we get;
784000 = 83600(T2-25),
T2-25 = 9.379,
So, T2 = 34.4,
Guys please try to solve this. The correct value for cp is 4180
By 1st law of thermodynamics;
Energy neither be created nor destroyed, it can be transformed from one form to another form.
So,
For 500 turns.
mgh = mcp( T2 - T1),
500*40*9.8*4 = 20*4180( T2-25),
By solving these we get;
784000 = 83600(T2-25),
T2-25 = 9.379,
So, T2 = 34.4,
(43)
Harika said:
3 years ago
Thankyou @Muhammed Ishaq.
(2)
Mohd Kasid said:
3 years ago
Thank you everyone for explaining the answer.
(2)
Emeka Udokwu said:
10 years ago
The potential energy of the falling body is converted to heat energy which will be gained by the water. The potential energy of the falling body is given by m*g*h = 40*9.81*4.
Since this is repeated 500 times, the total potential energy becomes 500*40*9.81*4 = m*cp (T1-T2). The mass of water and initial temperature is given and the heat capacity is known. Now solve for the unknown. Hope it's clearer @Yadav.
Since this is repeated 500 times, the total potential energy becomes 500*40*9.81*4 = m*cp (T1-T2). The mass of water and initial temperature is given and the heat capacity is known. Now solve for the unknown. Hope it's clearer @Yadav.
(1)
RAJ KUMAR said:
8 years ago
Thermodynamics first law - energy conversation ( energy can not create and can not destroy but it convert one form to another form).
mgh = mS (t2-t1).
(500*40)*9.81*4 = (500*40+20)*4.2*(t2- 25).
t2= 34.4.
mgh = mS (t2-t1).
(500*40)*9.81*4 = (500*40+20)*4.2*(t2- 25).
t2= 34.4.
(1)
Melese said:
6 years ago
nmgh = mcpdt.
dT = T2-T1.
dT = T2-T1.
(1)
Hiren bhatt said:
7 years ago
Please explain in detail I'm not understanding this.
Samuel A said:
1 year ago
Thank you for giving an explanation.
N.B. Parmar1753 said:
3 years ago
Thanks @Manu.
Ashish Yadav said:
4 years ago
Thanks everyone for explaining it.
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