Subject: Vapor Jet Pumps as Bottoming Cycle Refrigeration Cycle

From: David Wells <[email-masked]>
Date: Mon, 20 Oct 1997 19:23:25 -0700

Hey, all you thermodynamophiles:

Has anyone got any information as to references that I can refer to to
compute the efficiency of a cooling cycle using a Venturi vapor-jet
ejector as a pump?

The idea is this: you boil a material such as Freon 134a or butane at
about 60 C, send the high pressure gas to a "vapor ejector", which is a
handy little pump that I can buy in McMaster-Carr for a hundred bucks or
so,  said vapor ejector uses steam or other vapors to create a vacuume
with a converging/divergind sonic or supersonic nozzel, and then I use
the vacuum to evaporate the refrigerant gas.

The problem: modeling the thing.  The best I can do now is to use
Perry's Encyclopedia of Chemical Technology (see "ejectors"), which has
some performance curves to get pressure ratios given input compression
ratio of the motive gas.

Anybody out there ever made a "vapor jet refrigerator" ? How well did it
work?  How do you select the working fluid?

Geeze, after the virtually zero response to my "where's the beef" memo,
I'll bet this one gets a virtual zero.  

Not that I'm a pessimist....

-Dave

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From: [email-masked] (CONPUTE)
Date: 21 Oct 97 02:46:16 GMT

David Wells ([email-masked]) wrote:
: Hey, all you thermodynamophiles:

: Has anyone got any information as to references that I can refer to to
: compute the efficiency of a cooling cycle using a Venturi vapor-jet
: ejector as a pump?

: The idea is this: you boil a material such as Freon 134a or butane at
: about 60 C, send the high pressure gas to a "vapor ejector", which is a
: handy little pump that I can buy in McMaster-Carr for a hundred bucks or
: so,  said vapor ejector uses steam or other vapors to create a vacuume
: with a converging/divergind sonic or supersonic nozzel, and then I use
: the vacuum to evaporate the refrigerant gas.

: The problem: modeling the thing.  The best I can do now is to use
: Perry's Encyclopedia of Chemical Technology (see "ejectors"), which has
: some performance curves to get pressure ratios given input compression
: ratio of the motive gas.

: Anybody out there ever made a "vapor jet refrigerator" ? How well did it
: work?  How do you select the working fluid?

: Geeze, after the virtually zero response to my "where's the beef" memo,
: I'll bet this one gets a virtual zero.  

: Not that I'm a pessimist....

: -Dave

Do you have WWW access?

I have been studying Jet Pump design for a rocket engine.  I do have a few
useful WWW pages if you are interested.

                       Earl Colby Pottinger

 ----------------------------------------------------
 : Come play Realms of Despair! http://www.game.org :
 ----------------------------------------------------

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From: David Wells <[email-masked]>
Date: Tue, 21 Oct 1997 13:52:30 -0700

J. Forbes wrote:
> 
> In article <[email-masked]> David Wells <[email-masked]> writes:
> 
> If that vapor jet pump is the kind I'm thinking of, it has two inlets, and one
> outlet....not too useful for your intended application, as it would mix the
> refrigerant with the steam.
> 
> Jim

Jim-
I think you missed my point...

The vapor jet uses a single fluid, on both the inlet, the pump, and the
mix outlet.

What I am suggesting is that the heat from the photovoltaic array, be it
concentrating or non-concentrating, is collected and used to BOIL the
SINGLE REFRIGERANT.  This hot, high pressure (not that high pressure)
gas is directed into the vapor jet inlet. It is the PUMP fluid.

Next, suppose there is a LOWER PRESSURE EVAPORATOR, which is boiling at
a lower temperature, say around 45 or 50 deg F.  The boiled vapor is
then PUMPED OUT by the momentum of the jet. 

The outlet fitting would have the mixed streams, and would be at some
intermediate temperature and pressure.

Got it?

The vapor jet refrigeration cycle is not very efficient, and used only
if there is an abundance of some sort of waste heat, which I think we
have here, especially if the pv array type is the concentrating type,
such as a parabolic linear trough.

-Dave

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From: [email-masked] (J. Forbes)
Date: 21 Oct 1997 08:44:00 -0700

Jim