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Question

(a) Name the common refrigerent. How does it deplete ozone layer ?

(b) What is the alternative of chlorofluoro carbon ?

(c) State the advantages and disadvantages of using ammonia as refrigerent ?

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Solution

(a) Chlorofluorocarbons (CFCs): Refrigerants that Cause Ozone Layer Depletion How CFCs Destroy Ozone Layer

When the CFC refrigerants are leaked from refrigeration or air-conditioning systems, they drift around the lower layers of the atmosphere. Slowly they start infiltrating into the upper layers of the atmosphere and soon reach the ozone rich stratosphere, where they undergo major chemical changes.

(b)
The interim replacements for CFCs arehydrochlorofluorocarbons (HCFCs), which deplete stratospheric ozone, but to a much lesser extent than CFCs. Ultimately, hydrofluorocarbons (HFCs) will replace HCFCs. Unlike CFCs and HCFCs, HFCs have an ozone depletion potential (ODP) of 0.

(c) As a refrigerant, ammonia has four major advantages over CFCs and HCFCs:

  • An ammonia-based refrigeration systems costs 10-20% less to build than one that uses CFCs because narrower-diameter piping can be used.
  • Ammonia is a 3-10% more efficient refrigerant than CFCs, so an ammonia-based system requires less electricity, resulting in lower operating costs.
  • Ammonia is safe for the environment, with an Ozone Depletion Potential (ODP) rating of 0 and a Global Warming Potential (GWP) rating of 0.
  • Ammonia is substantially less expensive than CFCs or HCFCs

There are two key disadvantages to using ammonia as a refrigerant:

  • It is not compatible with copper, so it cannot be used in any system with copper pipes.
  • Ammonia is poisonous in high concentrations. Two factors, however, mitigate this risk: ammonia’s distinctive smell is detectable at concentrations well below those considered to be dangerous, and ammonia is lighter than air, so if any does leak, it will rise and dissipate in the atmosphere.

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