Thanks very much for all that effort, Overmod. [:P]
I was aware that the air pressure inside a boiler being filled would increase, and that if the pressurized air were used to enable the blower, it would have to be constantly monitored and adjusted. I wondered if the density of compressed air vs even 60 psi of steam was so little in comparison that the desired effect wasn’t practicable. I think you’ve explained that atmospheric air would not do, but that one or two specific gasses might, and I thank you for that.
As I was reading, I pictured heating elements because you mentioned water heaters, and I thought…why not? They’d require a catenary and panotograph, but it wouldn’t be nearly as efficient as traction motors, nor as cheap. Still…kinda neat to think about it.
It was done in at least one place, in a service I’d have thought would work reasonably well, in Switzerland during WWII. (This came up quite recently in another thread in one of the Kalmbach forums, with detail and pictures)
The installation was predicated on the existence of near-free hydropower and scarcity of various factors to build straight-electric locomotives to use it. This was a switch engine in intermittent duty, so there was a reasonable possibility that running the elements constantly would provide effective ‘enough’ overall heating if the elements couldn’t be made to approximate combustion gas heating; the situation is also potentially that for a fireless cooker, where the elements would only have to heat the ‘renaining’ water to make up for heat abstracted to do work in the cylinders rather than keep boiling fresh cold feedwater as in a conventional boiler. In the event, I have never seen the actual experiment described as anything but a failure.
The amount of resistance heating to do the job ‘promptly’ is staggering, especially by comparison with modern straight electrics. Remember that 35kW I mentioned that could hold 300psi? That’s for an isolated and thoroughly lagged vessel. Tap off even a little mass flow for auxiliaries and the required heat rate soars. Remember also that we’d be retaining many of the inefficiencies of combustion-fired reciprocating (or turbine or turboelectric) power, down in the dismal single-digit regions even with quick power modulation even at high heating rate… so power would have to be too cheap to meter,
