From: "Phil Scott" 
Newsgroups: alt.building.construction alt.home.repair alt.hvac misc.consumers.house
Subject: Re: Central Air v. Window-unit Air?
Date: Sat, 6 Aug 2005 02:02:27 -0700


"PrecisionMachinisT"  wrote in 
message news:GKednfkEn9Ns9GnfRVn-pg@scnresearch.com...
>
> "Phil Scott"  wrote in message
> news:dd1pfm$5le$1@news.tdl.com...
>>
>> Phil Scott
>> HVAC contractor/ mech engr since 1905
>>
>
> So your 100 years old now ??


    Satire.   Willis Carrier didn't come up with refrigerated 
AC until the 1905's or something like that..   Earlier we had 
steam jet refrigeration (a high pressure steam venturi side 
port, at approx 28" water column (vacuum) was connected to a 
large evaporating tank, water evaporate and cooled to 40F or 
so and that was pumped around to air coils... prior that that 
goes back to BC egypt, importing ice from Mt Kilimanjaro, into 
deep caves the cool air circulated through the palace.

The Montgomery Ward Store in Sacramento Calif though had an 
ammonia chilled water system as late as 1967 that I am aware 
of, it was still operating the last time I worked on it. It 
dated from the turn of the century 1915 as a guess..  Two 50 
ton baker 200 rpm reciprocating compressors driven by 
synchronous  DC motors..(multple coils around a rotor, looks 
like an old radial airplane motor.)

The Budweiser micro breweries built in the 70's used similar 
machines, approx 4,000 tons total of horizontal Baker 
reciprocating compressors, 200 RPM DC sychronous motors.. 
ammonia.

Why you might ask?   Ammonia is the most efficient refrigerant 
bar none in those temp ranges.  by a very wide margin.  and 
because... volumetric efficiency goes way up with the ultra 
long stroke and proportionately reduced head space volume of 
those huge slow long stroke compressors.  The suction lines on 
those plants were 24" main header... 10" to each of the Baker 
recips.

Latest addition though were 1000 hp Frick screws (made in 
Germany).

These are 3 stage cascade/ compound systems.. two compound 
ammonia stages, the lowest stage ammonia evaporator acting as 
the condenser for a CO2 system to
minus 110F...(200 hp of Vilter reciprocating compressors, 1750 
rpm, 480volt conventional squirel cage motors... all built 
nicely into one large machine building ( 300' square approx) 
with natural gas fired boilers...so that if there is a 
suitably sized ammonia leak, to the explosive limit ranges, 
the boiler pilots lite off the vapor cloud and make for 
interesting times in the vicinity..releasing about 8,000 lbs 
of ammonia to the atmosphere.

The CO2 as liquified at -110F under pressure for use in 
carbonating the beer..(not 100% naturally carbonated that 
stuff)



With large scale ammonia systems there are issues of liquid 
slugs in long suction lines, with pressure behind them and 
suction pressures approaching zero psig ahead of them.. slug 
velocity can reach over 700 mph.   Such a 'slug' of liquid 
hits an elbow or end cap and blows it off ... releasing the 
entire charge of ammonia to the atmosphere. clearing the 
sinuses of a few thousand people it doesnt kill and pissing 
off the local authorities entirely...most older systems were 
not built with the super sonic slug scenario in mind.

Now a question?   What do you think happens to an all steel 
ship, with frozen storage holds 6 decks deep, below the water 
level, with only the outside of envelope of the holds 
insulated, not the steel plates between the holds...those 
welded solid of course across the hull.

Thats exciting.


Phil Scott












Phil Scott

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