This document presents the CryoCar, which utilizes liquid nitrogen in an open Rankine cycle for automotive propulsion. Liquid nitrogen offers advantages over batteries in performance and cost. The system works like a steam engine, using a heat exchanger to boil liquid nitrogen which is then expanded in an engine to produce power. Analysis shows the liquid nitrogen cycle can provide competitive specific energies to lead-acid batteries. A modified Honda CRX using the liquid nitrogen cycle could achieve an energy density of 54-87 W-h/kg of nitrogen with a operating cost of $0.039-0.024 per km. The document concludes liquid nitrogen propulsion warrants further consideration due to advantages in refueling time compared to batteries.

1. CRYOCAR
PRESENTED BY
SIDDHARTHA BHATTACHARJEE
DEPARTMENT OF MECHANICAL
ENGG.

2. INTRODUCTION
Cryogens are effective thermal storage media which, when
used for automotive purposes, offer significant advantages over
current and proposed electrochemical battery technologies, both in
performance and economy. An automotive propulsion concept is
presented which utilizes liquid nitrogen as the working fluid for
an open Rankine cycle. The principle of operation is like that of a
steam engine, except there is no combustion involved.
The usage of cryogenic fuels has significant advantage over
other fuel. Also, factors such as production and storage of
nitrogen and pollutants in the exhaust give advantage for the
cryogenic fuels.

3. LN2000 LIQUID NITROGEN PROPULSION CYCLE

4. HEAT EXCHANGER
The heat exchanger is like the radiator of a car but
instead of using air to cool water, it uses air to heat
and boil liquid nitrogen. The resulting high-pressure
nitrogen gas is fed to an engine that operates like a
reciprocating steam engine, converting pressure to
mechanical power. The only exhaust is nitrogen, which
is the major constituent of our atmosphere.

5. POWER CYCLE
State 1 is the cryogenic liquid in storage at 0.1 MPa and 77 K. The liquid is pumped up to
system pressure of 4 MPa (supercritical) at state 2 and then enters the economizer. State 3 indicates
N2 properties after it is being preheated by the exhaust gas. Further heat exchange with ambient air
brings the N2 to 300 K at state 4, ready for expansion. Isothermal expansion to 0.11 MPa at state 5
would result in the N2 exhaust having enough enthalpy to heat the LN2 to above its critical
temperature in the economizer, whereas adiabatic expansion to state 4’ would not leave sufficient
enthalpy to use. The specific work output would be 320 and 200 kJ/kg-LN2 for these isothermal
and adiabatic cycles, respectively, without considering pump work. These power cycles provide
specific energies competitive with those of lead-acid batteries.

6. PERFORMANCE OF A
MODIFIED HONDA
CRX(RANKINE CYCLE)
Process Adiabatic Isothermal
Pump Work: 6 kJ/kg-LN2 6 kJ/kg-LN2
Net Work Out: 194 kJ/kg-LN2 314 kJ/kg-LN2
Heat Input: 419 kJ/kg-LN2 750 kJ/kg-LN2
Energy Density: 54 W-h/kg-LN2 87 W-h/kg-LN2
LN2 Flow Rate:† 1.5 kg/km 0.93 kg/km
Operating Cost:‡ 3.9 ¢ /km 2.4 ¢ /km
† Based on 7.8 kW for highway cruise at 97 km/h.
‡ Based on 2.6¢ per kg-LN2 production cost.

7. COMPARED TO
FOSSIL FUELS

8. Comparing Energy Densities:

9. TECHNICAL ISSUES
Range Extension and Power Boosting:
Range extension and performance enhancement can be
realized by heating the LN2 to above ambient temperatures
with the combustion of a relatively low pollution fuel such
as ethanol or natural gas. By increasing the gaseous N2
temperature to 500 K, the specific work at 4 MPa for the
adiabatic engine is increased by 60% to make it nearly the
same as the work from an isothermal expansion engine
operating at 300 K. In this particular propulsive cycle an
extra superheat of 200°C results in only a 30% increase in
specific power. Thus the advantage of operating above
ambient temperature depends, on how isothermal the
expansion process can be made to be.

10. CONCLUSION
The potential for utilizing the available energy of liquid nitrogen
for automotive propulsion looks very promising. Time to recharge
(refuel), infrastructure investment, and environmental impact are
among the issues to consider, in addition to range and performance,
when comparing the relative merits of different technologies. The
convenience of pumping a fluid into the storage tank is very attractive
when compared with the typical recharge times associated with lead-acid
batteries. Manufacturing LN2 from ambient air inherently removes
small quantities of atmospheric pollutants and the installation of large-scale
liquefaction equipment at existing fossil-fuel power stations could
make flue gas condensation processes economical and even eliminate the
emissions of CO2.

11. WHY???
HOW????
WHEN?????
WHERE???????
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QUESTIONSSSSS…!!!!!?????