free frost heat exchanger for cryogenic automotive propulsion
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Transcript free frost heat exchanger for cryogenic automotive propulsion
FREE FROST HEAT
EXCHANGER FOR CRYOGENIC
AUTOMOTIVE PROPULSION
CONTENTS
• Introduction
• Liquid nitrogen propulsion system
• Test vehicle
• Schematic vehicle of equipment layout
• Economizer
• Ambient air heat exchanger
• Ambient air heat exchange development
• Design
• Temperature profile
• Alternative heat exchanger design
• Conclusion
INTRODUCTION
The cryogenic automobile is a ZEV.
Operates on the thermodynamic potential between
the ambient atmosphere and a reservoir of liquid
nitrogen.
The working fluid is a liquid nitrogen
A zero emission vehicle is required to produce no
smog-forming tailpipe or evaporative pollutants.
LIQUID NITROGEN PROPULSION
SYSTEM
Storage tank
Pump
Heat exchanger
Expander
Liquid nitrogen propulsion
system
TEST VEHICLE
Originally electric.
Operating on a pack of 14
lead acid batteries which
weighed over 450kg.
Construction is welded
frame with riveted body
panels entirely made up of
aluminum.
Olson Kubvan
SCHEMATIC OF VEHICLE
EQUIPMENT LAYOUT
Liquid nitrogen storage tank
(Dewar)
Pressurization system
Economizer
Ambient air heat exchanger
Vehicle equipment layout
ECONOMIZER
Actually a pair of shell-and-
tube heat exchangers.
Operate in parallel, with the
shell-side fluid being the
exhaust from the expander.
Economizer units with and
without shell
AMBIENT-AIR HEAT EXCHANGER
Made up of 45 copper finned-tube
elements.
Elements are manifolded together.
Make a staggered array of tubes in
cross flow with the incoming air.
Either the motion of the vehicle,
or the two ducted fans located at
the back of the van.
Ambient-air heat exchanger
assembly
AMBIENT-AIR HEAT EXCHANGER
DEVELOPMENT
To design a heat exchanger that can operate in a
variety of environmental conditions and structurally
robust not being hampered by the build up of frost.
Dealing with frost formation fall into two categories:
1) PASSIVE CONTROL.
2) ACTIVE CONTROL.
PASSIVE CONTROL
Passive control involves either
preventing frost formation or over
sizing the heat exchanger such that
frost build up is unimportant on time
scale characteristic of automotive
travel.
ADVANTAGES
• Mechanical simplicity
• Reliability
DISADVANTAES
In general, less flexible in dealing
with off-design operation.
ACTIVE CONTROL
Active control of frost formation entails
allowing frost to become attached and
then removing it either thermally or
mechanically.
ADVANTAGES
• More operationally reliability.
• Much less dependent on the ambient or
operational conditions, responsive to
different loading condition.
DISADVANTAGES
Power consumption.
Poor-long term reliability.
DESIGN
The operating environment of a typical automobile
can be a demanding one.
There are weather conditions such as rain, snow, or
extreme heat to contend with.
There are driving conditions such as rough
pavement, gravel roads, potholes and speed-bumps.
Finally , automobiles have to meet rigorous safety,
comfort, and reliability.
TEMPERATURE PROFILE
The black arrows represent heat
transfer from the ambient air to
the wall.
The exterior wall temperature is
dependent on the heat transfer
coefficient and fluid temperature.
when the outside temperature is
lower than the freezing point of
water, frost will form.
when the ambient temperature is
above the freezing point of water,
if the temperature difference from
the air to the wall is too large .
Temperature profile of free
frost heat exchanger element
ALTERNATIVE HEAT EXCHANGER
DESIGN
A heat exchanger has been
developed which uses rotating
brushes for active frost-control.
This heat exchanger consists of
several multi – pass tubes
sandwiched between two sets of
concentric rings.
The cryogenic fluid (either liquid
or gas ) flows through the tubing
running in cross flow with the
ambient air.
Heat exchanger employing
active frost removal
CONCLUSION
The cryogenic automobile is a potential contest in the
ZEV market, provided certain key technologies are
demonstrated.
One of these technologies is the development of an all
- weather heat exchanger system.
A heat exchanger that works well in a variety of
operating conditions, is structurally robust, and is not
hampered by the buildup of frost is a necessary
technology for the cryogenic automobile.
REFERENCES
www.google.com
www.wikipedia.com
THANK YOU