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Calculation Formula of Cooling Capacity of Water Chiller and Analysis of Common Unit Name

ClassificationIndustry News NEWS 54

In the process of using the chiller, we found that the cooling capacity unit of the chiller has a variety of names, such as kcal, cold ton, BTU and so on. Today, Davossi will come with you to understand the calculation standard of the cooling capacity of the chiller and the conversion between each unit name.

1. Commonly used units of cooling capacity

The cooling capacity reflects the cooling capacity of the chiller, and we generally use 10,000 kcal/hour as the unit of measurement. The capacity of an industrial chiller is expressed in terms of heat absorbed from an object per hour, kcal/hr.
kcal is a unit of heat, that is, under standard atmospheric pressure, the heat required to increase the temperature of 1 kg of pure water by 1 °C is called 1 kcal.

In addition, it is often measured in cold tons (TR). Why use cold tons as cooling capacity? This is because natural ice was used for refrigeration before mechanical refrigeration devices were produced. Taking 1000kg (1 ton) of ice to melt into water in one day and night (24 hours), the average heat absorption per hour is the freezing unit, that is, the cold ton. The unit of cooling ton is convenient for estimating energy consumption and area of ​​air-conditioned area.
As a rule of thumb, 1 ton of cooling power needs to consume no more than 1 kilowatt (0.65Kw — 0.95Kw), and 1 ton of cooling capacity can cover an area of ​​20 square meters — 30 square meters.

2. the conversion of cold tons and kcal/hour

Because 1 cold ton (TR) is the average heat absorbed per hour for 1000kg of ice to dissolve into water in one day and night (24 hours). When 1kg of ice at 0°C becomes water at a temperature above 0°C, it needs to absorb heat, and its latent heat of fusion is 79.7kcal/kg.

So it is not difficult to calculate: 1TR = 79.7×1000÷24=3320kcal/hr

However, the British refrigeration unit is traditionally measured in pounds (ib), and is defined as the average heat release per hour of 2000ib of ice water from 32°F (0°C) to ice of the same temperature in 24 hours, defined as 1 US ton of cold.

Experiments have shown that to convert 1 pound of ice into 1 pound of water, 144 Btu (British Thermal Units) must be added.

Therefore: 1 US cold ton = 2000 pounds × 144 Btu/pound ÷ 24 hours = 12000 Btu/hr

And because 1Btu = 0.252kcal, so 1 American cold ton = 12000Btu/hr×0.252kcal=3024ktal/hr

3. What is cooling ton (heat dissipation ton)

The cooling capacity of 1 cooling ton is calculated under the conditions of circulating water volume 131/min – TR, inlet water temperature 37°C, outlet water temperature 32°C, and outside air wet bulb temperature 27wB.

H = M.C.△T (Note: Cooling water 11kg)

= 13kg/min×60hr×lkcal/kg.℃×(37 – 32)

= 3900kcal/hr

In the formula: H is the cooling ton TR; M is the flow rate per hour kg/hr; C is the specific heat of water kcal/kg; △T is the temperature difference between the inlet and outlet.

4. What does the EER of the chiller mean?

ERR is the energy efficiency ratio

Example: If the cooling capacity is 3800 kcal/hr and the power consumption is 1854W, the ERR is:

3800kcal/hr÷1854W=2.05kcal/W-hr

It consumes 1KW of electricity every 1 hour and can generate 2050kcal of heat.

5. Cooling water circulation

From the definition formula of cooling ton (CT), for example, when the temperature difference is 5℃, it can be obtained:

M (kg/hr)=3900kcal/hr÷1 kcal/kg.℃×5℃=780l/hr=131/min

If the temperature difference is 4°C, we can get:

M = 3900 ÷ 4=975l/hr=16.25l/min

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