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A liquid nitrogen vehicle is powered by liquid nitrogen, which is stored in a tank. The engine works by heating the liquid nitrogen in a heat exchanger, extracting heat from the ambient air and using the resulting pressurized gas to operate a piston or rotary engine.
Liquid nitrogen propulsion may also be incorporated in hybrid systems, e.g., battery electric propulsion and fuel tanks to recharge the batteries. This kind of system is called a hybrid liquid nitrogen-electric propulsion. Additionally, regenerative braking can also be used in conjunction with this system.
A liquid nitrogen economy is a hypothetical proposal for a future economy in which the primary form of energy storage and transport is liquid nitrogen. It is proposed as an alternative to liquid hydrogen in some transport modes and as a means of locally storing energy captured from renewable sources. An analysis of this concept provides insight into the physical limits of all energy conversion schemes.
Description
Currently, most road vehicles are powered by internal combustion engines burning fossil fuel. If transportation is to be sustainable over the long term, the fuel must be replaced by something else produced by renewable energy. The replacement should not be thought of as an energy source; it is a means of transferring and concentrating energy, a "currency" or energy carrier.
Liquid nitrogen is generated by cryogenic or Stirling engine coolers that liquefy the main component of air, nitrogen (N2). The cooler can be powered by renewable-generated electricity or through direct mechanical work from hydro or wind turbines.
Liquid nitrogen is distributed and stored in insulated containers. The insulation reduces heat flow into the stored nitrogen; this is necessary because heat from the surrounding environment boils the liquid, which then transitions to a gaseous state. Reducing inflowing heat reduces the loss of liquid nitrogen in storage. The requirements of storage prevent the use of pipelines as a means of transport. Since long-distance pipelines would be costly due to the insulation requirements, it would be costly to use distant energy sources for production of liquid nitrogen. Petroleum reserves are typically a vast distance from consumption but can be transferred at ambient temperatures.
Liquid nitrogen consumption is in essence production in reverse. The Stirling engine or cryogenic heat engine offers a way to power vehicles and a means to generate electricity. Liquid nitrogen can also serve as a direct coolant for refrigerators, electrical equipment and air conditioning units. The consumption of liquid nitrogen is in effect boiling and returning the nitrogen to the atmosphere.
Criticisms
Cost of production
Liquid nitrogen production is an energy-intensive process. Currently practical refrigeration plants producing a few tons/day of liquid nitrogen operate at about 50% of Carnot efficiency [1].
Energy density of liquid nitrogen
Any process that relies on a phase-change of a substance will have much lower energy densities than processes involving a chemical reaction in a substance, which in turn have lower energy densities than nuclear reactions. Liquid nitrogen as an energy store has a low energy density. Liquid hydrocarbon fuels by comparison have a high energy density. A high energy density makes the logistics of transport and storage more convenient. Convenience is an important factor in consumer acceptance. The convenient storage of petroleum fuels combined with its low cost has led to an unrivaled success. In addition, a petroleum fuel is a primary energy source, not just an energy storage and transport medium.
The energy density — derived from nitrogen's isobaric heat of vaporization and specific heat in gaseous state — that can be realised from liquid nitrogen at atmospheric pressure and zero degrees Celsius ambient temperature is about 97 watt-hours per kilogram (W-hr/kg). This compares with about 3,000 W-hr/kg for a gasoline combustion engine running at 28% thermal efficiency, 30 times the density of liquid nitrogen used at the Carnot efficiency
For an isothermal expansion engine to have a range comparable to an internal combustion engine, an 350-litre (92 US gal) insulated onboard storage vessel is required [2]. A practical volume, but a noticeable increase over the typical 50-litre (13 US gal) gasoline tank. The addition of more complex power cycles would reduce this requirement and help enable frost free operation. However, no commercially practical instances of liquid nitrogen use for vehicle propulsion exist.
Frost formation
Unlike internal combustion engines, using a cryogenic working fluid requires heat exchangers to warm and cool the working fluid. In a humid environment, frost formation will prevent heat flow and thus represents an engineering challenge. To prevent frost build up, multiple working fluids can be used. This adds topping cycles to ensure the heat exchanger does not fall below freezing. Additional heat exchangers, weight, complexity, efficiency loss, and expense, would be required to enable frost free operation
Safety
However efficient the insulation on the nitrogen fuel tank, there will inevitably be losses by evaporation to the atmosphere. If a vehicle is stored in a poorly ventilated space, there is some risk that leaking nitrogen depletes the level of oxygen in the air and causes asphyxiation. Since nitrogen is a colorless and odourless gas that already makes up 78 % of air, such a change is difficult to detect.
Cryogenic liquids are hazardous if spilled. Liquid nitrogen can cause frostbite and can make some materials extremely brittle.

Presented by:
Ravishankar

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I. INTRODUCTION
In 1997, the University of North Texas (UNT) and University of Washington (UW) independently developed liquid nitrogen powered vehicles in which the propulsion systems in these vehicles are cryogenic heat engines in which a cryogenic substance is used as a heat sink for heat engine.
Cryogenic:
Cryogenic can be defined as the branch of the physics that deals with the production of and study of effects and very low temperature.
Cryogenic Engineering:
It is mainly concerned with temperatures found in range of –150oC to absolute zero (-273.15oC).
Various Cryogenic Fluids:
 Liquid Helium
 Liquid Nitrogen
Cryogenic Heat Engine:
It is a engine which uses very cold substances to produce useful energy. A unique feature of an cryogenic heat engine is that it operates in an environment at the peak temperature of the power cycle, thus, there is always some heat input to the working fluid during the expansion process.
Physical Properties
• Molecular Weight: 28.01
• Boiling Point @ 1 atm: -320.5°F (-195.8°C, 77oK)
• Freezing Point @ 1 atm: -346.0°F (-210.0°C, 63oK)
• Critical Temperature: -232.5°F (-146.9°C)
• Critical Pressure: 492.3 psia (33.5 atm)
• Density, Liquid @ BP, 1 atm: 50.45 lb/scf
• Density, Gas @ 68°F (20°C), 1 atm: 0.0725 lb/scf
• Specific Gravity, Gas (air=1) @ 68°F (20°C), 1 atm: 0.967
• Specific Gravity, Liquid (water=1) @ 68°F (20°C), 1 atm: 0.808
• Specific Volume @ 68°F (20°C), 1 atm: 13.80 scf/lb
• Latent Heat of Vaporization: 2399 BTU/lb mole
• Expansion Ratio, Liquid to Gas, BP to 68°F (20°C): 1 to 694
Liquid Nitrogen :
Liquid Nitrogen is the cheapest, widely produced and most common cryogenic liquid. It is mass produced in air liquefaction plants. The liquefaction process is very simple in it normal, atmospheric air is passed through a dust precipitator and pre-cooled using conventional refrigeration techniques. It is then compressed inside large turbo pumps to about 100 atmospheres. Once the air has reached 100 atmospheres and has been cooled to room temperature it is allowed to expand rapidly through a nozzle into an insulted chamber. By running several cycles the temperate of the chamber reaches low enough temperatures the air entering it starts to liquefy. Liquid nitrogen is removed form the chamber by fractional distillation and is stored inside well-insulated Dewar flasks.
How does the Nitrogen Powered car work?
Heat from the atmosphere vaporizes liquid nitrogen under pressure and produces compressed nitrogen gas. This compressed gas runs a pneumatic (compressed gas drive) motor with nitrogen gas as the exhaust.
Main Components of the Engine:
 A pressurized tank to store liquid nitrogen
 A heat exchager that heats (using atmospheric heat) liquid nitrogen to form nitrogen gas, then heats gas under pressure to near atmospheric temperature.
 A pneumatic motor (along with a Volkswagen transmission) that runs the car.
Principle of Operation :
The principle of running the LN2000Car is like that of steam engine, except there is no combustion involved. Instead liquid nitrogen at –320oF (-196oC) is pressurized and then vaporized in a heat exchanger by ambient temperature of the surroundings air. This 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 major constituent of our atmosphere.
Analysis of CooLN2 Car Performance:
A single-cylinder reciprocating expander that runs on compressed nitrogen gas with the exhaust gas released into the atmosphere was considered. When compressed gas flowed into the expanders cylinder, isobaric work was done on the moving piston by the gas.
The net isobaric expansion work done during a single cycle is gauge pressure of the gas multiplied by the volume of the gas that flows into the cylinder.
The isobaric specific energy is Wi = (Ph-Pi)V= Ph(1-P-1)V
Ph-Pi is the difference in absolute pressure between inlet and exhaust gas.
If Pi is atmospheric pressure, Ph-Pi is the gauge pressure of compressed gas.
V is the volume occupied by the compressed gas per unit mass of gas.
P = Ph / Pi is inlet to exhaust pressure ratio.
The isobaric specific energy is Wi = RTh (1-P-1) /A.
Here Th refers to the temperature of the high pressure inlet gas.
The COOLN2Car which a converted 1973 Volkswagen and runs on liquid nitrogen is an illustrative to the use of isobaric expansion equation.
Open Rankine Cycle Process:
The processes considered are the expansion of nitrogen gas at 300K and 3.3 MPA to near atmospheric pressure. The first process considered is isothermal expansion from 3.3 MPA to 120KPA and the work can be easily computed as
Wisothermal = rT ln (P2/P1)
r = 0.2968 (KJ/KgK) for nitrogen gas and T = 300K.
The result for Nitrogen is 291.59 KJ/Kg. Another limiting process is the simple adiabatic expansion of the gas in which no heat is admitted during. the expansion. The work is calculated as
Wadiabatic = KrT [1-(P2 / P1) K-1/K] (k-1)
Where T = 300K and K = 1.4, the ratio of specific heats for nitrogen.
The resulting Wadiabatic is 180KJ/Kg of Nitrogen exhausted at 150KPA.
Advantages:
 The energy density of liquid nitrogen is relatively low and better than readily available battery systems.
 They have significant performance and environmental advantages over electric vehicles.
 A liquid nitrogen car is much lighter and refilling its tank will only 10-15 minutes.
 The exhaust produced by the car is environmental friendly.
Conclusion :
In a real sense, the more such vehicles are used, the cleaner the air will become if the liquefaction process is driven by non-polluting energy sources. In addition to the environmental impact of these vehicles, refueling using current technology can take only a few minutes, which is very similar to current gas refueling times.

pls send me full report and ppt.