Can I Recover Exhaust Heat by Using it to Pressurize Fuel From Inside Compartment

If you are intending to create a turbine driven fuel pump, certainly.

It will reduce fuel pump energy consumption while adding cost, complexity and potential maintenance issues. It will also create a potential exhaust restriction that may exceed the energy savings found at the fuel pump, and will have little or no effect at part throttle conditions. If used on a modern fuel injected gasoline powered engine the system will have to be after the fuel pump anyways (as these are usually submerged in the fuel tank), and may cause fuel pressure variations that play havoc with the fuel control if the pressure regulator can't keep up.

How much energy is your fuel pump consuming? Is the tank designed to hold the increase in pressure you are pondering?

Seems like this could get quickly expensive, with a less than reasonable chance of obtaining even a small net benefit.

There are other ways to make use of exhaust heat with far better chance of resulting in meaningful benefit.

This is just a design idea for a hardware that can be added to an engine (like turbocharger hardware). It could either be applied in car engine, jet engine, boat outboard motor, etc. Which type of engine I want to approach depends on which one would benefit from having such a hardware.

There is one guy who told me that outboard motor in the 50s like OMC uses pressure tank instead of fuel pump. So outboard motor is the most likely candidate. Since a lot of people are telling me that transferring heat could cause issue with vaporizing (vapor lock) and safety issue (autoignition), probably the transfer of energy should not proceed through heat exchange. Probably I will approach a mechanical energy transfer like through the use of impeller. Not really sure how that's gonna work. But thanks.

Most modern engines, even marine ones are now running fuel injection. A typical turbo charger boost is 7 psi, fuel injector pumps typically produce pressures of 60 psi and more, You're not going to help that along with a simple impeller pump.

hmmm... good point.. oh well, thanks annyways

There is plenty of power in the typical turbocharger to raise the pressure of the relatively small volume of fuel burnt to 60 psi. Remember the amount of air pressurized is quite large compared to the amount of fuel burnt in that air.

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The fuel pump doesn't use a lot of energy. It would be difficult to justify the cost of any changes given the tiny limit on any potential benefit.

Consider the bigger loads, the low hanging fruit. Alternator and the AC compressor can use a significant percentage of an automobiles total power. Using waste heat towards one of those ends has a lot more potential upside.

No.

Heating the fuel before the pump will result in cavitation issues, low fuel rail pressure, poor engine performance, and rapid pump failure.

The fuel pumps currently used are already designed for maximum efficiency.

I have witnessed a test vehicle that utilizes the waste heat from the exhaust flow in conjunction with an electric heating element (for cold-start assist) that vaporizes gasoline downstream of the fuel pump and stores the vapor in a heavy wall tank.

The vapor is then manipulated and injected into the cylinders using a modified direct injection delivery system.

The vehicle weighed in at 4800+ lbs. and testing results were promising with the high end of the miles-per-gallon DATA in the 60 MPG range and the low end at 35MPG.

The issues are with mitigating potential safety risk to the occupants and operator well enough to meet all NHTSA regulations.

Yes, yes. A very good idea. This is definately an aftermarket device particularly, and perhaps, only, suited for Cavaliers.

Heat in exhaust may be used to heat during winter or for refrigeration.

The most successful use of Exhaust heat recovery is to preheat the Fresh Air that contains oxygen and nitrogen. While oxygen is very useful for burning nitrogen is to be heated without any gain. Using the heat to raise the temperature by 125 deg C to 200 deg C is possible using Heat Pipe Technology. Each 22 deg drop in Exhaust saves 1% of fuel cost. The heat transfer is very balanced as the mass flow rates of flue gas and fresh air are almost equal and there is no moving part. I have done from 100 kW upto 1MW of heat in several cases. Cost will be around $100 to $ 160 per kW.

While the heat recovery can work in industry, I think it is not possible as far as the preheating of fresh air is concerned. The preheated air would mean less mass of air to engine and hence lesser oxygen and drop in engine performance. Any other views on this?

Maximum power will be reduced, but that doesn't necessarily mean lower efficiency. Efficiency increases are possible with warm air intakes. This is especially true for engines that control speed by restrictions airflow....pumping losses are lower at the same power with warmer air because the throttle does not need to restrict as severely.