I'm not sure this would work in a regular dryer. The heat that a gas or electric dryer creates is quite a bit hotter than the maximum you could get out of a water to air heat exchanger.
The max water temp in a non pressurized system would be around 200-210* and maybe 220* in a pressurized system. I'm pretty sure that the flame or electric element creates heat somwhere above 300*.
I'm doing laundry this afternoon, so I'll put the laser thermometer to work and try to get a reading on the temperature inside the dryer's drum.
I have thought about using hot water for clothes drying, but I think would have to be a extra hot room with clothes lines and exhaust fans. But maybe the dryer is not a shot as I think it is. I'll know later today.
See Ya, still planning on a pilgramage for a load of bulk coal this summer.
Take care, Greg