Mechanical water heater
Mechanical water heater
(OP)
Can I heat water mechanically using something like a torque converter?
I have a diesel motor powering a hydraulic pump for various work. I also want a supply of hot water. I will take what heat I can from the diesel motor's water jacket and exhaust, but if my water still isn't quite to desired temperature I'd like to provide the last energy maybe by turning a torque converter fixed at other end, then collecting heat from oil to water heat exchange.
Is there any merit in this idea?
I have a diesel motor powering a hydraulic pump for various work. I also want a supply of hot water. I will take what heat I can from the diesel motor's water jacket and exhaust, but if my water still isn't quite to desired temperature I'd like to provide the last energy maybe by turning a torque converter fixed at other end, then collecting heat from oil to water heat exchange.
Is there any merit in this idea?





RE: Mechanical water heater
But one wouldn't think this is the easiest way to get this job done. If the engine has an alternator, an electric resistance heater will do the same thing but without adding as much complication to the system.
RE: Mechanical water heater
I'd like to idle the engine when hydraulic demand is low and there is little work to do.
So a problem with using an alternator is when I have big demands is when the engine is revving slowest.
Back to taking heat from existing hydraulic power pack:
The torque converter might be totally unnecessary. Can I simply have a choke in my main hydraulic circuit with a heat exchange soon after it? A thermostat control of the choking device would govern my water temp.
Will the oil in the system suffer at this choke? Maybe need replacing much more often than normal because I'm generating 10kW by squeezing it?
RE: Mechanical water heater
RE: Mechanical water heater
But I wondering why web searches of "mechanical water heater" and "hydraulic water heater" etc aren't showing me where others have done this.
Maybe they do it but don't bother publish! Or maybe people seldom have plenty of hydraulic power while little or no electric power (at same time as need for hot water.)
Or maybe I'm unaware of problems with creating heat in the hydraulic oil. Am wondering if the oil loses viscosity or something - will the system need (normally) excessive oil changes?
I've found a hydraulics forum... I'll see what they say.
RE: Mechanical water heater
If the waste heat from the engine is not sufficient for what you are doing, it's probably more efficient to get a dedicated gas-fired heater ...
RE: Mechanical water heater
How about using a marine diesel fired water heater such as available from:
http://www.itrheat.com/waterheater.html
RE: Mechanical water heater
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Mechanical water heater
The thing is, I need a hydraulic powerpack regardless of water heating requirements. It will have a dedicated marine diesel of about 40kW. I'll get a good start on my heating requirements by using waste from the engine.
Then I'm after a neat solution, easily controlled by a thermostat, to "top up" the water heat requirement.
This might be as simple as having a coil of water pipe in the hydraulic oil tank that will extract heat from the oil, then deliberately forcing the heat of the oil to temperature required - about 43C I think.
I can't really see energy waste in this concept and I'm buying little equipment that wasn't needed anyway. But I don't know if the hydraulic system will appreciate the temperature and friction I would induce. Say I wanted 10kW of heating... it just sounds like a lot of energy shifting from mechanics to liquid (is that mechanical to latent??) in a small place... can I do that or will I wreck something?
Thanks for the tip on the water brake dyno.
I haven't heard anything from a hydraulics guru yet.
RE: Mechanical water heater
RE: Mechanical water heater
But then I must consider also, as soon as whatever "top up" heat generator kicks in because of lack of load on motor, then load increases and less "top up" is needed.
I don't think I can easily provide pto for a large alternator on this power pack. There are manufacturer's limits on pto from the front of the engine, and the bell housinging end is hogged by pumps. An alternator might also be an undesirably heavy option if I can instead use hydraulics I mostly already have.
So.... I'm keen (as you may have noticed
I calculated that I need about 22kW to take 10 l/m of sea water from 10C to 43C. It would be interesting to know efficiency of engine at different revs and then my potential efficency at harnessing the inefficiency. That figure of 10 kW "top up" above was a guess.
Thanks for the input, people.
RE: Mechanical water heater
RE: Mechanical water heater
I didn't get a close enough look to notice whether sea water cooled the engine directly in a once through loop or if sea water cooled an engine coolant loop which then cooled the engine/heated the hot water tank.
Either way the water coming out of the tank was hot enough to scald.
I would think that the diesel on your boat generates enough waste heat that you most of the way to supply 10 l/m of hot water to your diver. Not sure what the EGT on an idling diesel is but since you want to get creative, you could have a small tank, pass your coolant through a loop inside the tank, pass your exhaust gasses through a second loop, and provide a electric resistance heater as a backup in the event you can't get the desired heat input.
Depending on the length of the dives, you might be able to get away with a stored hot water system: The whole time you're steaming away to the dive site, the tank is being heated by waste heat so that when you get to the site you have 150 liters of 60C water. As you begin to dispense the hot water, incoming 10C water is heated as close to 43C as thermodynamics allow and so it will take awhile for the bulk temperature in the water tank to fall below 43C. Downside is added weight.
Found this sketch on Wikipedia
http:/
Might be right up your alley... good luck!
RE: Mechanical water heater
Hydraulic systems try to keep fluid cool. It seems that this might end up being a balancing act which keeps you dancing on the razor's edge between keeping it warm enough to heat the water, but also trying to keep the hydraulic fluid from overheating.
Interesting problem, though.
Engineering is not the science behind building. It is the science behind not building.
RE: Mechanical water heater
If I want water at 43C then we know the oil must be at least this temperature (actually it will be more - some thermal gradient is needed) when it leaves my heat exchange.
So I must consider how well my hydraulic circuit will behave at this sort of temperature. The resovoir, pump, ducting, etc will all need be kept insulated at a bit better than 43C lest I WASTE energy by letting it cool other than into my water.
When the 43C oil passes my point of restriction it will get hotter and should go next to the heat exchange.
Somebody mentioned water brakes above. And I started this thread thinking about a torque converter. These would be ways of generating heat after putting power through a hydraulic motor; the larger hydraulic circuit of the poerpack would remain unheated.
But so much more gear! Just heating the main circuit could be so simple if the circuit didn't mind. I'm guessing it would need to operate at about 48C. I don't know enough about hydraulics yet but I'm going to drive a mechanic mad with this stuff real soon.
RE: Mechanical water heater
You may drive a mechanic mad very soon, but eventually, implementation of your planned arrangements will likely give you much more distress. I wish you well, but I very much doubt the practicality of your ideas.
Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.