By Jim Taylor, Editor MACS ACtion Magazine
In spite of all the advertising, the internal combustion engines that we know and love are staggeringly inefficient. At root, they are just heat pumps, converting the heat of the combusted fuel into the mechanical motion of the piston. The problem is that only about a quarter of the available energy is converted to motion and the rest is thrown off as waste heat.
Engines are happiest and most efficient only within certain temperature ranges, and that’s why we have cooling and exhaust systems – to deal with the excess heat and gases from both the fuel process and internal friction. All that heat gets carried away from the engine block and released elsewhere into the atmosphere via either tailpipe or radiator. It’s been that way for a hundred years.
But times are changing and we’re entering an era of stiffly increased fuel mileage requirements and equally stiff emission reduction laws. One way to achieve both goals is to reduce the friction of moving components and fluids and get the engine warmed up sooner.
During a cold start, say January in Colorado or Vermont, the fluids in the engine, power steering and automatic trans have roughly the consistency of cold ketchup; they are very thick (viscous) and resist flowing. Some percentage of the engine’s power has to be used just to overcome that resistance, which in turn reduces fuel efficiency.
So, engineers wondered, how do we warm up and thin out those fluids so the engine can get down to business quicker? Using some of that waste heat quickly came to mind, and several major suppliers are now working on small coolant heat exchangers that are used to pre-warm various fluids. The units are small and easily mounted. Most are simply plate and tube construction and they route the warm fluid adjacent to the cooler one, letting thermodynamics do the rest.
Dana Corporation calls theirs the Active Warm-up heat exchanger; it comes complete with a built-in thermal bypass valve so the fluid does not continue to be heated when it reaches normal operating temperature. Look for this on the 2013 Ram truck, where it diverts a bit of the coolant to the transmission to help the ATF reach operating temperature more quickly. A similar unit is scheduled to appear on some Ford products next year.
Chrysler says that fuel economy on the truck with the trans heater is up by two percent (Dana achieved even higher test results on other vehicles), and that the unit may appear on other Chrysler vehicles in the future. That’s a relatively huge gain from a fairly simple unit, and one that can be adapted to preheat other fluids as well.
Dana Corp’s Active Warm-up heat exchanger
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