Living organisms use water not only as a source of nourishment but also as a refrigerant. The water that animals drink helps to regulate the body temperature by dissipating heat. When you also take a bath, you also regulate your body temperature, especially when you take a cold bath during a hot day.
Manufacturers are also constantly looking for environmentally friendly refrigerants to cool machines. A good alternative that has been there for many years is water, otherwise known as R-718 in the refrigerant industry. But when you compare water with other refrigerants (especially synthetic ones) is it a better option?
Well, if you want to find an answer, here’s what our experts at Refrigerant HQ believe.
Can You Use Water as a Refrigerant?
The short answer: Water, often referred as R-718 in the refrigerant industry, is a natural refrigerant used as a primary & secondary refrigerant in various AC systems. It is a good refrigerant since it is stable, non-toxic to the environment, cost friendly, and non-flammable. It’s also easy and safe to handle.
Here’s a summarized fact sheet on R-718.
| Name: | R-718 |
|---|---|
| Name - Scientific: | hydrogen oxide |
| Name (2): | Water (distilled water) |
| Name (3): | Steam |
| Classification: | Natural Refrigerant |
| Chemistry: | H2O |
| Status: | Active & Growing |
| Future: | Will Be Used All Over The World |
| Application: | Industrial Heat Pumps |
| Application (2): | Refrigeration plants, Compressor pumps |
| Replacement For: | CFCs, HCFCs, and now HFCs |
| Ozone Depletion Potential: | 0 |
| Global Warming Potential: | 0 |
| Global Warming Risk: | Very Low |
| Toxicity Levels: | A (No Toxicity Identified.) |
| Flammability Levels: | Class 1 - No Flame Propagation |
| Lubricant Required: | MO, AB, POE |
| Boiling Point: | 99.9743 °C or 373.1243 K or 211.9537 °F |
| Critical Temperature: | 373.946 °C or 647.096 K or 705.1028 °F |
| Critical Pressure: | 22, 060 KPa |
| Triple Point | 0.0100000000000477 |
| Molar Mass: | 18.02 g/mol |
| Density: | 322 kg/m3 |
| Melting Point: | −187.7 °C; −305.8 °F; 85.5 K |
| Vapor Pressure: | 853.16 kPa (at 21.1 °C (70.0 °F)) |
| Manufacturers: | Various Including: Honeywell, Chemours, Arkema, Mexichem, Chinese, etc. |
| Manufacturing Facilities: | All Over Including: USA, Mexico, EU, China, and others. |
| Form: | Liquid & Gas |
| Color: | Colorless |
| Odor: | Odorless |
| EPA Certification Required: | No |
| Require Certification to Purchase? | No |
| Cylinder Color: | Unknown |
In recent years, countries and companies have been looking for refrigerant replacements that are friendly to the environment.
Traditional refrigerants such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) contained chlorine, which is a chemical that had a high ozone depleting potential (ODP). Countries through the Montreal Protocol had to find a way to eliminate these refrigerants because the long term result would be disastrous if manufacturers continued using it.
Again, Hydrofluorocarbons (HFCs) came in to replace CFCs and HCFCs since they had a lower ODP. However, the problem with these refrigerants was that they had a high global warming potential. Countries had to meet again to find a way to regulate the use of these chemicals. Now, it’s 2023 and the HFC phaseout is already in motion after countries signed The Kigali Agreement.
In the process of finding a suitable refrigerant replacement, manufacturers started using natural refrigerants again. Generally, these are substances occur naturally in the environment. Other than water (R-718), some common examples of natural refrigerants include Ammonia (R717), Carbon Dioxide (R-744), Air (R729), Oxygen (R-732), among many others.
Some common applications of water as a refrigerant are:
- It is useful in evaporative coolers
- Used in data centers to cool servers
- Ideal for absorption chillers
- Used in cooling towers as a primary medium of heat dissipation in power plants, industrial processes, and AC systems
- Used in ice production for refrigeration purposes
- Steam ejector refrigeration
Why R-718 is a Good Refrigerant
From 2023 going onwards, we should expect to see more manufacturers and industries using water (R-718) as a refrigerant. Why, you may ask?
1. It is Eco-friendly
This is the first reason why water is a good refrigerant. Most of the refrigerants in use today are very regulated because they are not environmentally friendly. For instance, HFC refrigerants (such as R-134A, R-404A, R-410A, etc) have high a global warming potential. Most HFCs will no longer be in use by 2032 because if we don’t stop using them, the earth will become even warmer.
For water, it occurs naturally within the environment; in fact, 71% of the earth’s surface consists of water. Our bodies, too, consists of 66% of water. Hence, in case the refrigerant escapes into the atmosphere during an installation, repair, or maintenance, it shouldn’t be disastrous like in the case of other natural refrigerants.
Also, R-718 is odorless. There’s no way to smell it if it leaks out of a heating or cooling device. However, this also presents another problem, which we will discuss in another section in this article.
2. Water Has a High Heat of Vaporization
Heat of vaporization (otherwise referred to as the enthalpy of vaporization or latent heat of vaporization) refers to the amount of energy needed to transit from a liquid state to a gas/vapor state. In this case, it’s the energy needed to convert water (the refrigerant) into a vapor state.
Note that a good refrigerant should be able to convert from liquid to gaseous state and vice versa readily at moderate pressure. Water has a high heat of vaporization of 540 Cal/g. This makes it easy for the refrigerant to absorb a lot of heat as it boils, which helps to achieve a proper cooling effect for your device.
3. It Is Readily Available
When buying or replacing a refrigerant, you need to consider several factors such as demand and supply, manufacturing costs, government regulations, transportation costs, use, etc. Refrigerants become expensive if:
- Demand and supply is low
- The manufacturing costs are high
- There are strict regulations on specific refrigerants
- Transportation costs are high
HFC refrigerants, such as R410A, are expensive because there’s less production for these refrigerants. You cannot find them easily since governments are limiting their use because of their global warming potential.
On the other side, just like most of the natural refrigerants in the market, water is readily available. You can find it almost anywhere, there are no strict regulations on how you should use it, and you don’t have to spend so much if you want to replace it. That means operation and energy costs for systems that use water as a refrigerant are low since they don’t use a lot of power/electricity to cool a space.
4. Easy to Handle
Another notable benefit of using water as a refrigerant is that it’s easy to handle. In case of a leak during installation, repair, or refrigerant replacement, the refrigerant will not harm anyone if you get in contact with it or if you inhale it.
Further, it’s not flammable like Ammonia. There have been many incidences where ammonia leaks have caused substantial damage.
Additionally, water is:
- Non corrosive
- Chemically stable
Limitations: Why Isn’t Water Used as a Refrigerant?
Although water is a great refrigerant, it also has a few undesirable elements/characteristics that make it a less preferred refrigerant.
The two main reasons why this is the case:
- Water has a high boiling point
- It also has a high freezing point
With these two qualities, it would mean that manufacturers have to find a way to lower the pressure within the compressor to lower the boiling point. You’ll, therefore, need a large compressor unit to achieve this, eventually leading to increased operational costs and inefficient systems.
Another limitation that may only be a problem during a leakage is that R-718 is odorless. Normally, most refrigerants in the market have an odor they so that you can detect them before they can harm anyone or damage a property.
In summary: Here’s a simple comparison chart we made to help you compare the pros and cons of using water (R-718) as a refrigerant.
Wrapping Up
From the article, we can conclude that water is a good natural refrigerant since it’s chemically stable, economical, non-toxic, non-flammable, and easy to handle. However, it may not be suitable in certain heating and cooling applications because of its high boiling and freezing point.