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