Heat Exchange in a Vehicle Engine System

A compressed natural gas engine system comprising a heat exchanger, the heat exchanger comprising:

• a first fuel port at a first end of an elongate heat exchanger body;
• a first heat transfer fluid port at the first end of the elongate heat exchanger body;
• a second fuel port at a second, opposite end of the elongate heat exchanger body;
• a second heat transfer fluid port at the second end of the elongate heat exchanger body;
• a fuel flow path that is straight between the first and second fuel ports;
• a heat transfer fluid flow path that is straight between the first and second heat transfer fluid ports, the heat transfer fluid flow path being parallel to, and beside, the fuel flow path;
• a heat transfer wall between the fuel flow path and the heat transfer fluid flow path;
• a first plurality of fins extending from the heat transfer wall into the fuel flow path;
• and
• a second plurality of fins extending from the heat transfer wall into the heat transfer fluid flow path.

A natural gas engine fuel heating method comprising:

• communicating natural gas fuel through a fuel flow path in an elongate heat exchanger body, the fuel flow path being straight between a first fuel port at a first end of the elongate heat exchanger body and a second fuel port at a second, opposite end of the elongate heat exchanger body;
• communicating liquid heat transfer fluid through a heat transfer fluid flow path in the elongate heat exchanger body, the heat transfer fluid flow path being straight between a first heat transfer fluid port at the first end of the elongate heat exchanger body and a second heat transfer fluid port at the second end of the elongate heat exchanger body, the heat transfer fluid flow path being parallel to, and beside, the fuel flow path;
• and
• transferring heat between the liquid heat transfer fluid in the heat transfer fluid flow path and the natural gas fuel in the fuel flow path by a heat transfer path between the heat transfer fluid flow path and the fuel flow path, the heat transfer path including a heat transfer wall between the heat transfer fluid flow path and the fuel flow path, fins that extend into the heat transfer fluid flow path from the heat transfer wall, and fins that extend into the fuel flow path from the heat transfer wall.