Posted bySuper Radiator Coils on Mar 10, 2022 9:56:32 AM
Our Refrigerant Focus series delves into the history, properties, suitable applications, and pros and cons of some of today’s popular or otherwise noteworthy refrigerants. This installment will focus on R-290 (propane). Check out some of our refrigerant focus posts below. R-290, commonly known as propane, is used for low-to-medium temperature refrigeration applications like freezers and refrigerated display cases, and has a lengthy history as a refrigerant. In fact, along with natural refrigerants like ammonia (R-717) and isobutane (R-600a), propane played an instrumental role in our early understanding of the compression and expansion-based cooling process that laid the foundation for modern refrigeration equipment. The first commercially available propane refrigeration equipment was developed in the 1930s, coinciding with the emergence of synthetic refrigerants like R-12. These new refrigerants - and the dozens of subsequent formulations that would follow - became the standard, and efforts to find additional uses for R-290 fizzled out. It remained a popular option for small-scale refrigeration applications (vending machines, refrigerators, etc.) and industrial processes, but few others. However, along with natural refrigerants like CO2, propane refrigeration is experiencing something of a renaissance, as manufacturers continue the search for high-performance refrigerants that comply with today's regulations. Today, R-290 is used as a low-global warming potential (GWP) replacement for refrigerants R-22, R-404, & R-134a for certain applications. R-290 is a single-component hydrocarbon substance. It's a byproduct created during the refinement of natural gas and petroleum. The most notable of propane's properties is its flammability More properties for R-290 can be found in the table below. R-290 Properties Formula Molecular weight (g/mol) 44.1 Boiling temperature°F (°C) -43.8 (-42.1) Critical temperature°F (°C) 206.1 (96.7) Critical pressure, PSI, (Bar) 616.5 (42.5) Global Warming Potential 3 Ozone Depletion Potential ASHRAE Safety Group A3 For a performance comparison, we’ve run a theoretical 36” x 70” 2-rowcondenserthrough our coil selection software,Enterprise. The coil’sairsideandtube-siderequirements are below and thecoil’s rating is below that. The design conditions are shown below along with the performance rating for that coil using R-290, R-22, R-404A and R-134a. Airside Tube-side Air flow 4,000 SCFM Condensing temp. 135°F Target capacity 165,000 Btu./hr. Hot gas temp. 180°F Entering air temp. 90°F Leaving air temp. 55°F/45°F (WB) Air pressure 14.696 PSIG Performance Comparison: R-22 vs. R-290 R-22 R-290 Difference (%) Difference (abs.) Coil capacity 186,478 Btu/hr. 180,537 -3.3% 5,941 Btu/hr. Leaving air temp. 107°F 106.4°F -0.5% 0.6°F Refrigerant pressure drop 6.59 PSI/coil 4.428 PSI/coil -49% 2.162 PSI/coil Refrigerant mass flow 2,481 lb./hr. 1,243 lb./hr. -49.9% 1,238 lb./hr. Performance Comparison: R-134a vs. R-290 R-134A R-290 Difference (%) Difference (abs.) Coil capacity 188,375 Btu/hr. 180,537 Btu/hr. -4.1% 7,838 Btu/hr. Leaving air temp. (WB) 107.1°F 106.4°F -0.7% 0.7°F Refrigerant pressure drop 6.922 PSI/coil 4.428 PSI/coil -36% 2.494 PSI/coil Refrigerant mass flow 2,465 lb./hr. 1,243 lb./hr. -49.6% 978 lb./hr. Performance Comparison: R-404A vs. R-290 R-404A R-290 Difference (%) Difference (abs.) Coil capacity 185,669 Btu/hr. 180,537 Btu/hr. -2.8% 5,132 Btu/hr. Leaving air temp. (WB) 106.9°F 106.4°F -0.5% 0.5°F Refrigerant pressure drop 6.156 PSI/coil 4.428 PSI/coil -28% 1.728 PSI/coil Refrigerant mass flow 3,169 lb./hr. 1,243 lb./hr. -61% 1,926 lb./hr. Note: The same circuiting was used for all three coils. The main benefits of R-290 are: Propane features a drastically lower GWP than R-404A, R-22, and R-134A, which is the primary reason that R-290's usage has increased in recent years as a replacement for those older, environmentally harmful substances. The main drawback of R-290 is: While 500 grams is very low as far as refrigerant charges are concerned, propane is an excellent "pound for pound" refrigerant, and equipment with refrigerant charges of that size can still be very effective. Refrigerants like R-290 are good fits for small-diameter tube, like SRC's 5mm product. There's less refrigerant involved and therefore less tube material is needed, allowing coils to be smaller, which saves space and potentially reduce costs. If you're designing a system and can't decide which refrigerant is the best option, drop us a line.We have multiple refrigerant experts on staff that can help you make the right choice to get the most out of your heat transfer equipment. Don’t get left out in the cold when it comes to heat transfer information. To stay up to date on a variety of topics on the subject,subscribe to The Super Blog, our technical blog,Doctor's Orders, and follow us onLinkedIn,Twitter,andYouTube.History of R-290 as a Refrigerant
Properties of R-290
C3H8 Performance Comparison of R-407A vs. R-404A & R-22
Inputs Subcooling degrees 5°F Pros & Cons of R-290
R-290: Pros
As illustrated in the performance comparison above, R-290's performance is very comparable to those of R-22, R-404A, and R-134a. But you'll notice the refrigerant mass flow needed to meet the theoretical requirement is much lower for R-290 than the others, which could lead to lower refrigerant costs. R-290's pressure drop in the theoretical application above (4.428 PSI/coil) is 49% lower than an identical coil running R-22 and 36% lower for the same coil running R-134a, resulting in reduced wattage consumption.R-290: Cons
So, based on the performance comparison, propane seems like a no brainer, right? Not exactly. As we touched on in the properties section, ASHRAE has designated R-290 as a class A3 refrigerant, its highest flammability classification. As a result, there's been hesitancy in the industry to apply propane for functions like building HVAC due to the potential consequences of leaks, and until recently ASHRAE had assigned a charge limit of 150 grams to the refrigerant. However, there's been a push in recent years to explore other uses for R-290, and ASHRAE has proposed increasing its charge limit to 500 grams.
