Natural Refrigerant - Hydrocarbon

Hydrocarbons are refrigerants that can be used as an alternative to fluorocarbon
refrigerants in some refrigeration and air conditioning applications.
The term ‘Hydrocarbon’ encompasses following:
 A) Ethane (R170)
 B) Propane(R290)
 C) Butane (R600)
 D) Isobutane (R600a)
 E) Propylene (R1270)

Properties
1) Hydrocarbons are highly flammable.
2) They have a low toxicity.
3) Hydrocarbon refrigerants are fully compatible with nearly all lubricants commonly used
    in refrigeration and air conditioning systems. One major exception to this rule is
    lubricants containing silicone and silicate.

Comparison with HCFC
1) HVAC professionals have made a comparative study on the performance of hydrocarbon
    refrigerants R290, R600a and R1270 with that of HCFC refrigerant R22 and found that in
    comparison to R22, hydrocarbon refrigerants have similar or better ability.
2) An experiment on a new refrigerant blend comprising R134a (an HFC) and hydrocarbon
    refrigerants R600a and R290, with a view to finding a replacement for the CFC refrigerant
    R12 in domestic refrigerators. The experiment concluded that the blend has been identified
    as a promising alternative to be used as a refrigerant in a conventional R12 system and
    that the blend reduced energy consumption by 4 to 11%.
3) Hydrocarbon refrigerants generally are compatible with the materials used in systems
    designed for R22 and often can use the same or similar lubricants, however, their
    substitution requires significant attention to safety issues including application
    specific considerations.
4) It has been observed that no (one) refrigerant has been identified as a suitable
    alternative for most applications,though they identify that some refrigerant blends “offer
    good options”. Blends can be HFC/HFC or HFC/HC.
5) Hydrocarbons may be suitable in some applications, and may not be in others, so every
    application needs to be carefully assessed on its merits.

Safety Issues
1) As mentioned above, hydrocarbon refrigerants are flammable and therefore certain
    restrictions are placed on their use to ensure safety.
2) All electrical contacts must be sealed or non-sparking.
3) The refrigerant charge in a system below ground level must not exceed 1.0 kg.
4) Sealed systems not exceeding 0.25 kg can be sited in any location.
5) Systems with charges exceeding 0.25 kg must not be located anywhere where a sudden loss
    of refrigerant will raise the concentration in the room or occupied compartment above the
    practical limit (0.008 kg/m³)
6) Piping for systems exceeding 1.5 kg must be restricted to the room containing the
    refrigerant.
                       

Hospitals, prisons, theaters, supermarkets, schools, hotels, restaurants, dwellings	• Refrigerant charge must not exceed 1.5 kg per sealed system • Refrigerant charge must not exceed 5.0 kg in special machinery rooms for indirect systems
Offices, small shops, small restaurants, places for general manufacturing and where people work	• Refrigerant charge must not exceed 2.5 kg per sealed system • Refrigerant charge must not exceed 10.0 kg in special machinery rooms for indirect systems
Industrial, cold stores, dairies, abattoirs, non public areas of supermarkets	• Refrigerant charge must not exceed 10.0 kg in humanly occupied spaces • Refrigerant charge must not exceed 25.0 kg for systems with high pressure side in special machinery rooms • No restrictions are placed on the charge size if all parts of the system containing refrigerant are in a special machinery room or in open air

Corporate Acceptance
1) In Europe, many models of domestic refrigerators are charged with hydrocarbon
    refrigerant in the factory. It is estimated that there are at least 100,000,000 household
    refrigerators in use around the world containing hydrocarbon refrigerants.
2) Hydrocarbons have also been used in small air conditioning systems and cold drinking
    water dispensers.
3) Hydrocarbon refrigerants are also commonly used in large process refrigeration systems
    in the oil and gas industries.

Natural Refrigerant - Carbon dioxide

The use of Carbon dioxide (R744) as a refrigerant declined for a number of reasons, including
changes in technology and the introduction of fluorocarbon refrigerants, which were seen
as ‘safety refrigerants’.

Properties
A) Carbon dioxide has an ozone depletion potential (OPD) of zero and a global warming
     potential (GWP) of 1.
B) It is generally regarded as a cheap and easily available refrigerant, and many regard
     it as an ideal refrigerant.
C) Carbon dioxide is non-toxic. It has low toxicity and is non-flammable.
D) Carbon dioxide is colorless, odorless and is also heavier than air.If enough carbon
     dioxide builds up in an enclosed space it will begin to displace oxygen and can cause
     asphyxiation in anyone present within the space. As carbon dioxide is colorless and
     odorless, a person in the space will not be able to tell unless proper detectors and
     alarms are installed.
E) As a refrigerant, carbon dioxide operates at a higher pressure than fluorocarbons and
     other refrigerants. While this presents design challenges it can usually be overcome in
     systems designed specifically in suction and discharge tubing.
F) Carbon dioxide is not compatible with commonly used refrigeration system lubricants.It
     is not suited for use with polyol ester (POE) and poly vinyl ether (PVE) lubricants, and
     it has only limited applications with poly alkylene glycol (PAG) lubricants.

Safety Issues
A) Some restrictions are placed on the size of the refrigerant charge, with additional
     allowances made for systems with detectors and alarms fitted, and as carbon dioxide is
     heavier than air the standard requires “suitable precautions” to be taken to prevent the
     undue accumulation of refrigerant in occupied spaces in the event of a leak.
B) As with fluorocarbon refrigerants, the standard also requires the system to be designed
     to withstand the refrigerant’s maximum operating pressure.
C) The International Institute of Refrigeration (IIR) identified carbon dioxide’s high
     working pressure as the main drawback to its use.


Thermodynamic Properties
1) Carbon dioxide is colorless. At low concentrations, the gas is odorless. At higher
     concentrations it has a sharp, acidic odor.
2) At standard temperature and pressure, the density of carbon dioxide is around 1.98
     kg/m3, about 1.5 times that of air.
3) Carbon dioxide has no liquid state at pressures below 5.1 standard atmospheres (520
     kPa). At 1 atmosphere the gas deposits directly to a solid at temperatures below −78.5 °C
     and the solid sublimes directly to a gas above −78.5 °C. In its solid state, carbon
     dioxide is commonly called dry ice.
4) Liquid carbon dioxide forms only at pressures above 5.1 atm; the triple point of carbon
     dioxide is about 518 kPa at −56.6 °C.The critical point is 7.38 MPa at 31.1 °C.

Corporate Acceptance
Coca Cola company stated that the company’s preliminary field tests proved the technology
to be reliable, in real life circumstances the equipment often used less energy than
equivalent equipment using HFC as a refrigerant.
Till 2006, the company was market testing a range of drinks fridges and vending machines
using carbon dioxide refrigerants.

Natural Refrigerant - Ammonia

Most of the refrigeration and air conditioning equipments in the world today uses
fluorocarbon refrigerants to facilitate the heat transfer process. Fluorocarbon
refrigerants are synthetic chemicals which causes a high global warming potential,
and are a greater threat to the ozone layer as well if released to the atmosphere.
There are alternatives to these HFC's that can help to mitigate some of the
environmental risks.These are called ‘natural’ refrigerants because
the substances also occur in nature, these alternatives are:
   1) Ammonia,                                               
   2) Carbon Di Oxide
   3) Hydrocarbons

   Ammonia (R717)
   Ammonia is a naturally-occurring substance that can
   be used as a substitute to fluorocarbon refrigerants in
   refrigeration systems.


 
Properties
A) Ammonia (NH3)- R717 is a colorless gas with high pungent smell at atmospheric
     pressure, and possesses the ideal environmental properties for a refrigerant – it has
     both a zero ozone depletion potential (ODP) and a zero global warming potential (GWP).
B) These properties make ammonia an attractive prospect as a refrigerant, given that
     fluorocarbon (HFC) refrigerants can have global warming potentials as high as 3900.
C) Many people are familiar with ammonia as an ingredient in fertilizers and other products.
     Ammonia carries a B2 safety classification, meaning that it has a high toxicity, and also
     carries a medium flammability risk.
D) Ammonia is not compatible with commonly used refrigeration system lubricants.
     It is not suited for use with polyol ester (POE) and poly vinyl ether (PVE) lubricants,
     and it has only limited applications with poly alkylene glycol (PAG) lubricants.

Safety Issues
A) A glass of drinking water can contain as much as 1mg of ammonia, a 200gms steak
     as much as 13mg, and some food additives can contain as much as 18mg.Cigarette
     smoke and even the air we breathe also contains ammonia in small amounts.
B) This demonstrates that the human body can deal with ammonia in small quantities.
     Generally, any amount in the atmosphere below 20 parts per million (ppm) is regarded
     as not dangerous. At amounts of up to 53 ppm, ammonia’s characteristic odor will be
     noticeable.
C) In amounts of 300-400ppm, prolonged exposure will become unpleasant, and in amounts
     over 700ppm it can cause burns and serious damage to eyes. In amounts of 5000ppm or
     above,exposure can be lethal to humans within five minutes.

Thermodynamic Properties
A) Vapor mass is lighter than air ( 0.6 compared to air 1.0).
B) Ignition will occur at 651 C when vapor concentration is between 15% and 28%.
C) Ammonia corrodes galvanized metals, cast iron, copper, brass & copper alloys.
D) It weighs 5.15 pounds(2.34Kgs) per gallon(3.78 Liter) in liquid conditions
     (water weight 8.33 pounds per gallon).
E) Boiling point of liquid ammonia at atmospheric pressure is -2.22 C.
F) Liquid ammonia expands 850 times its liquid volume at atmospheric pressure.

Room Air Conditioner - EPS/Thermocol

EPS often called as Thermocol is designed keeping in mind the excellent thermal insulation and low cost.When assembled inside the window air conditioner it gives an excellent mechanical fastening to the partition plate and evaporator.Usually the density of the designed components is kept at 30 kg/cu.m and the granular size is 5 mm.