Tone of refrigeration

A ton of Refrigeration (TR)

A ton of refrigeration (TR)  is a unit of heat extraction capacity of the refrigeration or cooling equipment. Generally, TR is defined as the amount of heat transferred to freeze or melt 1 short ton of ice at 0 deg. C in 24 hours. 

1 TR is approximately equal to 12000 BTU or 3024 Kcal/hr of energy/heat load. 

The heat of the fusion of water is about 335 KJ/kg or 80.01 kCal/kg. 1 short ton is equal to 2000 lb or 907 kg. 

                      

 Example: 1000 kg/hr of air is to be cooled from  45 deg. C to 10 Deg. C in the heat exchanger with chilled water for some process requirement then what will be chiller capacity required. Temp. the difference across the chiller is assumed to be 5 deg. C. The chilling water is pumped through a heat exchanger using a centrifugal pump. The Chiling circuit is as below,

Ans:

TR is the amount of heat to be extracted from the system or process.

Assumption :

1.     Air is 100 % dry at inlet temp.

2.     The system is well insulated and Heat gain from the atmosphere is negligible.

Here cooling duty of the heat exchanger is the amount of heat to be extracted and heat added by a chilling water recirculation pump.

Let's calculate the Chilling duty (Q_a) of the heat exchanger.

Qa     = Air Flow rate x Cp of Air x ( Air in temp – Air out Temp)

          = 1000 x 0.24 x ( 45-10 )

          = 8400 Kcal/hr

Qa = 8400/3024 = 2.78 TR ------------------ I

Let's calculate the chilling water flow rate (Mw) for Qa

Chilling water flow rate (Mw)  = Qa /( Cp x ( Chiller temp. Diff.)

Mw = 8400 /(1*5) =

Mw = 1.7 m3/hr ------------------------ II

Pumping power (Shaft power) with about 30-meter liquid head and 30 % pump efficiency is about 0.44 kWh. Assuming worse case that all pumping power  (Qp) will be added to liquid which is about 0.44 kWh i.e. 378 kCal/hr ( 1 kWh = 860 Kcal).

Total heat load on chiller is,

 Qc    = Qa+Qp

          = 8400 + 378

          = 8778 Kcal/ Hr ------------------------------ III

Chiller Capacity =  8778 Kcal/hr i.e. 2.9 TR.

Note:

1.     If air or gas is saturated or has moisture then the heat of condensation will be added to cooling duty to calculate actual chiller capacity.

         

Nature is full of inspirations and learnings irrespective of situations.

View from Malhar Hills, Dhayari, Pune( PC - Bharat Kadu)

We are been to Malhar hills on the 14th Oct 2018, a beautiful place adjacent to our residence. It's been a great outing for the team which has a member as young as 3 years to 50 years. We had a nice interaction which was full of information and ideas. The place is extremely beautiful and untouched by the urban culture which makes it very refreshing and energizing for young and adults. 

I would like to share a thought that passed by when we were coming down to base camp. It is the similarity between our life and the process of climbing up & down the hill.

Generally, when we climb up we have to fight against gravity and the odds of the place such as rocks, stiff slops, etc. Things are there to pull us down if we don't move up.  These things actually demand a fair amount of energy (physical & Mental) and we get tired. Still, we climb up to the summit. Basically, we prove our mental against all odds. In our life when we are determined for something we exhibit the same efforts to achieve our goals irrespective of situations around us, isn't it? Let me tell you it feels great when we accomplished those goals, right?. We thank all our hard work and supporters for the same. It's awesome, similar to learning from failure.

The situation when we are coming down from top to base. We need not put a lot of effort and energy as now flow is with us. I feel personally this is the most difficult situation one can face in life and it could prove one of the best teachers of all time. It is most difficult to control and keep yourself composed and determined when you succeed in something. It is very much similar to learning from our own success.

" Learning from the success is as important as from the failure"