Difference Between Ammonia & Freon Gas for Cold Storage

Comparison between refrigerants (ammonia vs Freon )

 1. Lower Costs

Ammonia is the cheapest refrigerant. The price per kg for R22 is about 2.5 times and R134a is about 7.0 times the price of ammonia. For a large cold storage, the operation costs are 20-30% lower with ammonia than R22. Besides that, only half as much material needs to be purchased to charge a system because the density of ammonia is half of halocarbons.

• Refrigerant Cost - Ammonia R717 - RM5/kg
• R22 - RM10/kg
• R134a - RM30/kg
• R404a/R507 - RM35/kg

Density of at 1.013bar at boiling point: 682kg/m3 (ammonia liquid), 1413kg/m3 (liquid R22) and 1376kg/ m3(liquid R134a).

 2- Better Coefficient of Performance (COP)

 Ammonia is up to 10% more efficient than other refrigerants. As a result ammonia systems use less electricity than other system.

• Ammonia R717 - 8.09
• R22 - 7.41
• R134a - 7.2
• R404a/R507 - 6.77

3. Higher Heat Transfer Coefficients

Based on the heat transfer correlations provided by ASHRAE Handbook of Fundamentals, the ratio of heat transfer coefficients for ammonia relative to R22 are:

• Condensation outside tubes: 4.1 : 1
• Condensation inside tubes: 3.5 : 1
• Boiling outside tubes: 1.6 : 1
• Boiling inside tubes: 2 : 1

 4. Better Efficiency –

  Due to its highly favorable thermodynamic properties (high latent heat of vaporization), ammonia requires less primary energy to produce a certain refrigeration effect compared to other commonly used refrigerants. Evaporating one pound of liquid ammonia absorbs about 161 Watts compared to 12 to 25 Watts for Freons.
Ammonia R717 - 1371.2 kJ/kg

• R22 - 233.95 kJ/kg
• R134a - 215.9 kJ/kg
• R404a/R507 - 208.0 kJ/kg

*Latent heat of vaporization (kJ/kg) is the heat absorbed when a substance changes phase from liquid to gas.

5. Smaller pipe dimensions required for the same refrigerant capacity

Ammonia requires smaller pipe sizes for a large system spread over a large area due to less drop in saturation temperature compared to Freon. In suction lines at the same drop in saturation temperature, a given pipe will provide 2 to 3 times more refrigerating capacity with ammonia than R22.

6. Immediate detectability of leaks
Ammonia has pungent odour and even small leaks are immediately detected. Many people refer to ammonia as "self-alarming"--you don't need a leak detector to determine that there is ammonia present. This is an important advantage over freon where large quantities could escape without detection. Ammonia leaks are found quickly and repaired.

7. Great tolerance to water contamination
Modest contamination with water does not usually interfere ammonia system operation. With ammonia, water stays in solution and does not freeze out and block orifices.
8. Environment friendly

Ammonia is an environmental friendly as it has zero Ozone Depletion Potential (ODP) and zero Global Warming Potential (GWP). It has no effect on ozone layer and no direct part on global warming.
       Ammonia R717 - 0 ODP, 0 GWP

• R22 - 0.034 ODP, 1700 GWP
• R134a - 0 ODP, 1300 GWP
• R404a/R507 - 0 ODP, 3784 GWP

9. Ammonia is not miscible with Paraffinic and Naphthenic Lubricants

This characteristic of non-miscibility makes lubricant management in ammonia systems quite simple. The very small amount of lubricant that escapes the lubricant separator will be released by the ammonia in the evaporator and it can be removed (drained) easily. This characteristic is ideal for industrial systems.