Time to stop using 404a?

[marinechiller]

I have been thinking along the lines of this article

http://www.racplus.com/features/-is-it-time-to-stop-using-r404a/8610668.article

for some time. Any comments about alternatives to 404a that give higher efficiency? Not looking for 2-3 percent better, but at least 10% better.

[pcvh1976]

Hi mate,

I think there is not any kind of refrigerant what is 10% better than the R-404a.
What is equal is the R407C, not much trouble in use to retrofit, only new oil and expansion valves. And in case you need more capacity (5-10%) use a heat exchanger. Good luck

[xxargs]

In coolpack and standard value (-10/+35 and 0.7 in isentrop eff)

around 8 percent better from R404A to R407C or R290

on R290 and if you have suction heat exchanger with liquid line and 70% termal efficiently, can make 11 percent better than R404A and in near R134a-level.

ie for 10 kW cooling power R404A draw 3406 Watt, R410A 3256Watt R407C 3180 Watt, R290 3146 watt, R290 with 70% suction gas heat exchanger 3067 Watt, R134A 3098 Watt, R600a 3072 Watt, R600a suction gas heat exchanger 70% eff, 2945 Watt. for R12/R134a pressure range DME (Dimethyl ether) have almost same efficient as R600a...

worst case of common synthetic refrigerant as R404A draw 3406 Watt in running - best natural refrigerant R600a with suction gas heat exchanger 70% eff, draw 2945 Watt - more than 400 Watt in difference for 10 kW cooling power.

in practical life many more thing influence result efficiency, if look on freezer and refrigeration on household - efficiency increase more than theoretic (up to 20 %) difference going from R12/R134a to R600a and none can explain really why...

[superslim007]

Have you looked at R407A? can be up to 20% more efficient, low GWP and apart from a small adjustment to your expansion valve you should be good to go

[xxargs]

R407A is still blend with R32 (20%), R134a (40%) and R125 (40%) and have more high GWP and low efficient R125 [1] compare to R407C (R32 23%, R125 25%, R134a 52%) - so I don't expect better theoretical COP than R407C, but little higher pressure and 0.5 C lower glide than R407C possibly fit better machine running R404A before...

[1] R125 working almost a heat adsorb-filler material in refrigerant blend to take down head temperature in case of high pressure difference between condenser and evaporator as freezer

but remember R407A have not so small glide (~6 degree C, ~3-4 degree practical in evaporator after expansion and cooling down condensate) compare to R404A have only 0.5 degree C...

[chillerman2006]

CO2 .... pressures seem a bit high at first but fine once you get used to it

Remember the panic of 410 pressures

[xxargs]

same as R290/R1270

I see now lot of new equipment in restaurants, in bar, beverage coolers and so on using R290 now, but before R404A was almost standard...

[marinechiller]

Firstly, thanks for all the replies. It seems others are thinking about this too.

I haven't looked into 290, 600, 1270, probable because with no experience they seem like a good way to blow something up (I'm guessing this isn't true, just the fear of unknown);)

I have used r22 and r434a which all give at least 10% better performance in my medium temp water chilling and heating applications. Availability and price have led to using 507 and 404.

But I am now selling based on efficiency (thank you government incentive program) and want to lead the pack on this. Seriously considering CO2. Going to run a test with r442 in the next weeks. My worry is the glide issue in our evaporator. Refrigerant supplier says it is not an issue in a single pass unit. We'll see. Unfortunately both of these options are more expensive than 404, but the incentive program helps. This is why I'm looking for 10% better, to make the extra capital more sensible to the customer. A 2-3% efficiency increase does not wow the customer into writing a bigger check on a 10-30 ton unit.

[marinechiller]

ie for 10 kW cooling power R404A draw 3406 Watt, R410A 3256Watt R407C 3180 Watt, R290 3146 watt, R290 with 70% suction gas heat exchanger 3067 Watt, R134A 3098 Watt, R600a 3072 Watt, R600a suction gas heat exchanger 70% eff, 2945 Watt. for R12/R134a pressure range DME (Dimethyl ether) have almost same efficient as R600a...

xxargs.... how do you arrive at these numbers? Seems like a great comparison method for refrigerants. I often do time consuming predictions/comparisons by plugging different gases into Copeland compressor performance tables.

[xxargs]

coolpack (free software from danfoss mm.) and NIST Refprop (not free and necessary for new refrigerants as HFO1234yf or blend of HC, DME etc. ) - is working on refrigerants enthalpy and entropy etc. same way you can make by hand with pt-chart and enthalpy/entropy-chart -but faster...

hardest factor to get is compressors isentropic efficiency and you still need compressors data sheet to make some own calculus to estimate isentropic efficiency, ie. isentropic efficient on compressor have very huge impact on systems COP...

You have also different factor is not can explain of thermodynamic difference of used refrigerant - for example going from R12/R134a to R600a giver around 20% better efficiency but if you look on enthalpy/entropy etc. give difference only 4% better for R600a compare with R12. Why - none really know, but i think lower viscosity, better vapor and liquid thermal condition in evaporator, condenser for R600a and possible big factor is lower absolute pressure make lower leak rate (in mass) trough sealing inside compressor. ie. leak inside compressors (piston in cylinder, scroll and sealing edge in rotary etc) for R410A and CO2 is pretty high and can be over 10% of swept volume in high pressure system (high mass trough sealings depend of high density of vapour) but almost non exist on low pressure system as R600a.

And even if swept volume for R600a compressor is lot bigger for same cooling performance, leaking in sealing not scale same degree as pumped volume increase (sealing area^2, pumped volume^3) and make lower leak rate per cc pumped volume...

[Peter_1]

http://www2.dupont.com/Opteon_Stationary/en_GB/assets/download/opteon-xp40-retrofit-guidelines.pdf is a good guide