X-Message-Number: 2152
Date: 23 Apr 93 21:23:25 EDT
From: Mike Darwin <>
Subject: Mechanical Refrigeration

From: Mike Darwin
To: Brian Wowk, All
Re: Mechanical Refrigeration
Date 22 April, 1993

     I  am  writing in response to Brian's comments about my  thoughts  on 
mechanical refrigeration.  I think what we have here is two different sets 
of working assumptions.  Probably I am at fault for not better  qualifying 
what I said.

     First, I am NOT opposed to good, reliable mechanical refrigeration as 
long  as a reliable heat sink material/refrigerant is used in  conjunction 
with  such  a system.  For instance, using a  mechanical  refrigerator  to 
liquefy or keep liquid a large reservoir of nitrogen would be  acceptable.  
If the refrigerator fails, you still have plenty of liquid nitrogen around 
and  what  is more, the system can be run by just having  liquid  nitrogen 
delivered.   I  am opposed to systems which rely  on  refrigeration  alone 
(such as the Queue) or which rely on refrigeration and a passive heat sink 
(such  as  lots of water ice) without the ability to plug in  a  delivered 
refrigerant such as LN2 if the refrigerator goes down.

     If  the Polycool system is as good as its manufacturers claim it  is, 
then  it  sounds  like  it  should  be  vigorously  pursued  and  used  to 
refrigerate  a  reservoir of LN2.  What I think would be  a  real  mistake 
would  be to use the refrigerator and a heat exchanger with  fans  blowing 
over it such as is used in conventional refrigerators -- even if you  have 
a lot of heat sink material like water ice lying around to buy you a  week 
or  two.  You never want to be under the gun to get the mechanical  system 
up  and running.  Redundancy, redundancy, redundancy is ever the  name  of 
the game.

     Re: Thermal Ballast.  My ten cents worth is that you don't want  lots 
of  small containers.  They will cost you a lot in time and you will  have 
to  have heavy lift capability anyway to move patients around.   Just  use 
drum  sized  used that interlock and move them around with  your  overhead 
"floor  crane."   Alternatively the facility could be designed  such  that 
the  ballast  spaces  are an integral part of  the  construction  and  are 
flooded and sealed during the building of the unit.  Patient cells can  be 
filled with patient pods filled with ballast material.  When it's time  to 
put  in  a  patient, you hoist up the pod and  insert  the  patient.   The 
"removed"  pod  then takes X days to thaw out and is ready  for  the  next 
patient to go into.  All of your other ballast is an integral part of  the 
construction.

     I  might add that using this kind of system has other  advantages  in 
that will allow you to use the ballast material as structural material  in 
some cases.  Dividers could be relatively flimsy until the whole system is 
filled  and  frozen.   Then the ballast  becomes  solid  and  structurally 
useful.   You know, ice is strong stuff.  I've trusted my life to it  both 
as  an  adult and a child more than  once (I can't swim).  If  it's  thick 
enough  you can even drive a car on it.  I hate to see all that  wonderful 
thermal  ballast material not being used to architectural advantage.   Now 
please  be  aware  that  I  an not  proposing  to  do  away  with  ambient 
temperature   stable  infrastructure  altogether,  just  save   money   by 
decreasing its beefiness.

     Finally,  all  those cans or bottles will add up to a  lot  of  extra 
cost.  And you DO NOT wants lots of small anything.  They invariably  turn 
into a real pain.

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