Transcript rw_7_31_07_poster.ppt

Liquid Nitrogen Freezer
Ryan Wood, Undergraduate Student
Clark Radcliffe, Faculty Ren Zhen, Graduate Student
Introduction
System Description
Calculations
Medical research depends largely on
storage of bio-materials. Without proper
storage units, materials can be ruined and
research will be set back. The goal of this
project was to develop a storage unit that is
cooled with liquid nitrogen and runs free of
electricity.
The system consisted of a small freezer
connected, by an insulated hose, to a tank of
liquid nitrogen. The flow of liquid nitrogen
into the freezer was regulated by a valve
and an actuator. The actuator was controlled
by a temperature meter which shut the valve
when the system became too cold; and
opened the valve when it became too warm.
A number of different calculations regarding
the thermal properties of the system were
performed. To collect data for the
calculations, the system was cooled to -75
degrees C with no contents, then was
allowed to warm up to around freezing. The
process was repeated with a known
quantity of thermal inertia in the form of ice.
Time and temperature data were recorded
in both cases. Then, by manipulating
several heat transfer equations, the thermal
inertia and heat transfer coefficient could be
calculated for the system.
Results
The results from the thermal calculations
were used to simulate experimental data. A
comparison was then done with actual data,
and it was concluded that the calculations
were in fairly good relation to the
experimental data. The graphs show the
temperatures in degrees C, as a function of
time, in seconds.
Simulation Data
Experimental Data
10
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0
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-10
-20
-30
Series1
-40
-50
-60
-70
-80