Refrigeration fundamentals:

1. Refrigeration:

It is a science of providing and maintaining temperatures below that of surrounding atmosphere.

2. Ton of Refrigeration (TR):

It is the quantity of heat required to be removed from one US tonne of water at 0 ⁰C (32 ⁰F) to freeze it to ice at 0 ⁰C (32 ⁰F) in 24 hours, because same cooling (refrigeration) effect will be given by uniform melting of the same ice.

One US tonne of water = 2000 lbs (pounds)

Latent heat of fusion of ice = 144 Btu / lb

Therefore,

 1 TR = (1x2000x144) / 24

            = 12000 Btu / hr

1 Btu = 1.055 kJ

Therefore, 1 TR = 12000 x 1.055 / 3600 = 3.517 kW

1 kcal = 3.968 Btu

Therefore, 1 TR = 12000 / 3.968 = 3024.2 kcal / hr

Note:

i. “ton” is unit of heat whereas “tonne” is a unit of weight.  

ii. “TR” unit is used in US, UK and India. In many other countries, standard MKS unit of kcal / hr is used

iii. Due to fact that refrigeration was first produced by ice, the refrigeration effect of refrigerating machines is compared with refrigeration produced by ice.

3. Coefficient of Performance (COP):

COP = Refrigerating effect / Work input

Relative COP = Actual COP / Theoretical COP

4. EER (Energy Efficiency Ratio):

EER = (Cooling capacity in Btu / hr) / (Power input in watts)

5. SEER (Seasonal Energy Efficiency Ratio):

The anticipated performance of a refrigerating device, over an average season is called as SEER and is expressed in same way as EER.

Note:

a.    COP is dimensionless whereas EER & SEER are not dimensionless.

b.    COP is important from designer point of view.

c.    EER is important from manufacturer point of view.

d.    SEER is important from customer point of view.

e.    EER = 3.412 x COP (In Btu system)

f.     EER = 3.6 x COP (in SI system)

Air conditioners have EERs ranging from 8.2 to 10.5. On the other hand, water cooled system has EER = 12 or even higher than this.

6. IPLV (Integrated Part load value)

In central air conditioning plants, water chiller is one of the main components.

IPLV measures the efficiency of water chiller under variety of conditions i.e. when the system is operating at various capacities such as 25 %, 50 %, 75 % and 100 % and at different temperatures. IPLV rating is given in kW / TR.

Hello HVAC engineers,

this blog is specially for each and every HVAC engineer who just wants to know about how an HVAC system works, I will help you out in learning the basics of HVAC design and each and everything you would love to know about HVAC.

So lets start with what is HVAC 

REFRIGERATION CYCLE

H- HEATING

V- VENTILATION

A- AIR

C- CONDITIONING

The figure indicates the components of a basic refrigeration cycle. It consist of 4 basic components

1. Compressor
2. Condenser
3. Metering device
4. Evaporator

so lets start with what is this refrigeration cycle and its working. The cycle is a closed loop cycle with basically four components, each of the component has its basic principle of working and its property

Compressor: It takes refrigerant vapour in from the low pressure side of the circuit, and discharges it at a much higher pressure into the high pressure side of the circuit.The compressor is the heart of the system; it keeps the refrigerant flowing through the system at specific rates of flow, and at specific pressures.The rate of flow through the system will depend on the size of the unit,And the operating pressures will depend on the refrigerant being used and the desired evaporator temperature.the compressor basically is used to create the pressure difference low temperature low pressure refrigerant .

Condenser: the objective of the condenser is to discharge the heat of the refrigerant and to change the vapour refrigerant to liquid refrigerant. the temperature of high pressure high temperature liquid refrigerant from the compressor is higher than that of the atmosphere here the condenser cools the refrigerant and brings it to liquid state.