Reverse Refrigeration Cycle (Organic Rankine)

[jbl300]

Hi.How can you get more pressure(250PSI),maybe with a bigger heat exchanger and let the pump running longer?R134?Thank you!

[jbl300]

Can you tell me please what brand is the feed pump?Thanks!

[jbl300]

Hi.If you change the air motor with a expansion valve and a evaporator it will be an air conditioner?It will work?Thank you!

[skittlesmonkey]

why is it that the Rankine Cycle is run with a liquid that has such a high heat of vaporization wouldn't u want to generate as much gas with as little heat as possible?

[skreennaim02]

R-123 was chosen as the refrigerant due to its low condensation temperature, which allowed the refrigerant to be transferred in liquid form at room temperature. High heat of vaporization is actually preferable here, as it reduces the required flow rate to extract the same amount of work from the heat source.

[skittlesmonkey]

wait isn't flow rate the thing that gives u energy? wouldn't u want as much gas as possible per unit heat energy to put more spin on the motor? if with 23 kj of heat energy i can make 22.4 liters of ammonia vapor or something like 30 liters of propane vapor and let them run past a pneumatic motor y would i choose the ammonia if i get more gas to utilize with the propane?

[skittlesmonkey]

i have read that high heat of vaporization is desirable but i don't understand why? why does it matter that the energy it took to make that gas is higher or lower when its rushing past a turbine and than being compressed.

[Membrane556]

I wonder if something like this could recover waste heat from vehicle engines.

[tsport100]

Yes they can... BMW are working on rankin cycle and thermocouples and new Hybrid rules at Le Mans for 2010 allow Organic Ranking energy recovery systems.

[terry1919]

so are you saying that if this system is part of a Nuclear generating plant you could extract more energy to use to drive another electric generator as well as a steam turbine????

[tsport100]

How are you 'estimating' the efficiency without generating any power off the output shaft?

That's a vane type pump, some companies offer turboexpanders that run at cryo temps in the low Kw range.

[skreennaim02]

The air motor comes with a chart that gives an estimate of the output power based on RPM of the shaft and pressure differential across the pump. RPM was measured using a stroboscope, pressure difference was measured using gauges seen in video (one on each side of the air motor).

[skreennaim02]

Correction to above: "pressure differential across the air motor"

[SWINGREGORY]

GREAT

[0tispunkm3y3r]

this air motor you talk about.... is it just a radially vaned compressor/turbine? is it like an automotive one?

can you remember how much power you got out of this system? this would be interesting to know given that your temperatures are in the same region as we have in a project we're working on as a final year project.

[davepetrie]

What did you use for the turbine?

[skreennaim02]

An air motor made by the Gast Corporation. Because it was not made for refrigerant, it had to be cleaned out and lubricated after operation. As far as our group could tell, no small scale refrigerant turbines exist, so we improvised.

[mrwebb7]

Can you explain a little bit better how this works.

[skreennaim02]

It is a Rankine cycle using R-123 as the working fluid. Heat is supplied by a water heater, to simulate a low grade (200 F) heat source, which vaporizes the refrigerant. Work is then extracted with a modified air motor before the gaseous refrigerant is cooled back into a liquid.

[mrwebb7]

Thank you. What did you use for a turbine? Curious if these system are only viable for large systems or could be scaled down to be affordable for residential application? How much did the pieces cost?

[skreennaim02]

This system is relatively small, approximate output is .3-.5 hp (none was captured here). The heat required to run it was a small water heater with the thermostat removed. I do not have exact numbers now. If you have access to refrigeration parts, one could be built for around about $500. The biggest costs would be a high pressure pump for the refrigerant, the air motor, and refrigerant itself.

[davepetrie]

I'm also interested to know what you used as the turbine.

Also what is your flow rate?

[skreennaim02]

The turbine is a Gast air motor. I do not recall exact rates as I do not have the technical literature anymore, but it is approximately 10-15 CFM of R123 at 170 degrees F.

[DeffRo]

i think hes putting a vacuum on it thats why its bubbling...he changing the boiling point.....i just got into the union :D

[skreennaim02]

No vacuum, it is boiling. That is refrigerant that has condensed around the sealed off drive shaft and is being reheated by the air motor casing.

[davepetrie]

Are you using a seperator and superheater after the boiler? or are you passing it directly through the air motor?

[skreennaim02]

directly through the air motor and into the condenser, had to replace all of the gaskets in the air motor, they were not originally compatible with R-123

[CaptainFreon]

I am not too sure how they came up with the term "reverse refrigeration cycle" for this. The actual definition of refrigeration is removing heat from one point and rejecting it to another. There system does not do that.

[d1ez3]

sweet

what is the source of the waste heat?

[skreennaim02]

For the experiment it was an electric water heater, ideally the system would replace a cooling tower at a nuclear plant.

[apeppink]

Carnot efficiency, assuming exhaust at ~ 60 deg. F. is (1-((60+460)/(190+460)))*100%~­20%. Seems like your efficiency estimate may be a little too hi.

[skreennaim02]

Did you read my comment below on the method used to calculate that efficiency?

[Yanosh457]

Maybe in the future they will make something like this for the condenser fans.

[costellogroup]

is that net 30% efficiency? even at delta t of 55 K doesn't the carnot max efficiency hit just 20%. i'm actually working on solar thermal to electric power through ORC.

[skreennaim02]

The 30% efficiency is based on: work out(estimated) - electricity used (for pump) / heat in (with proper regards to all units involved). What refrigerant will you be using as a medium? With R-123 we did not have much success until we were in the operating range of 180-190, heat your refrigerant as hot as you can get it before attempting to extract work out of it. Theory will get you far, but make sure you have a proper turbine (our biggest problem) to extract the work.