OT: Ice thickness sensing in ice bank

Hey all,

I'm looking for some sort of analog sensor that can sense the thickness of a layer of ice on a submerged pipe. We have an ice builder and I need to know what our cooling capacity is. After googling and coming up with nothing, I thought you guys might have some ideas.

Thanks,
Steve

i will come back on this better answer is at refrigeration engineer.com

Steve,

Someone at Tsinghua University, in Beijing, China invented a method in 2004, using the change in the RC (Resistance & Capacitance) between water and ice. See this link:

http://www.sciencedirect.com/science/article/pii/S1359431104003308

Is the heat transfer fluid a liquid or a gas?

If you can measure the flow of the heat transfer fluid and in/out temperatures you can compute the capacity. Liquids are easy to measure. Gas is a little harder (read more expensive) to measure. If the heat transfer fluid enters as a liquid and leaves as a gas the computation is a little harder but all you need to do is measure liquid flow and convert to mass flow.

I'm not sure what exactly an ice builder is. Is it some kind of ice maker the ejects the ice? If so then just weigh the ejected ice, measure its temperature, and measure the temperature of the feed water. That's all you need to compute capacity. If there is no feed water waste then metering in the feed water will work instead of weighing the ice.

TConnolly I had a health and safety girl tell me that ice could only get to 32 or maybe 31 F because that us where it changes states and it wouldn't get any colder than that. This was news to me I was always under the ASSumption that absolute 0 was the coldest anything could get I didn't know it was 31 F. I asked her if water was heated over 212 and u added 10 degreenthalupyes to it hot hot it would. You guessed it it can only get to 212 or 213 then it changes states.

Same girl we had a paint booth and all the hot air was sitting on the floor. The cold air was uparound the ceiling. Apparently the laws of physics change in that location in Louisville KY. It didn't have anything to do with the fact she was standing next2 to a 50 HP motor exhaust port from under the booth.

OK enough nonsense. How Are you measuring the sensible heat in the gases? Some type of enthalpy sensor?

TConnolly said:

Is the heat transfer fluid a liquid or a gas?

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It's a fluid, water.

TConnolly said:

I'm not sure what exactly an ice builder is. Is it some kind of ice maker the ejects the ice? If so then just weigh the ejected ice, measure its temperature, and measure the temperature of the feed water. That's all you need to compute capacity. If there is no feed water waste then metering in the feed water will work instead of weighing the ice.

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The ice builder is basically a large tank of water with coils of ammonia cooled pipe that accumulates ice. The amount of ice that we have determines how much cooling capacity that we have. The ice water is distributed through the plant and used for cooling in various processes.

This is similar to our ice builder:

http://www.chester-jensen.com/p_ice_builder.html

I'm looking for something that can sense how much ice that we have. Something analog and submersible.

Nit submersible but What about a laser or ultra sonic? How accurate do you need an thickness?

I don't think you will find an easy answer.

You could measure thickness of ice at one point with a radar or ultrasonic level transmitter possibly.

You could measure total quantity of ice by measuring the weight of the entire ice builder. Ice weighs less than water. Certainly not easy or cheap.

Steve,

OK, I see what you are asking now. I looks like you are looking for a way to determine how much stored refrigeration capacity (latent heat) you have in the form of ice that can be melted.


Ice weighs 57.23lbs*ft^-3 while water weighs 62.43lbs*ft^-3. If the volume is constant then mounting the tank on load cells might give you a means for determining ice/water ratio.



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Jeff, I'd like to meet her because if she is right I can think of several ways to make us all billionaires the likes of which even Gates and Buffet couldn't dream of.

TConnolly said:

Ice weighs 57.23lbs*ft^-3 while water weighs 62.43lbs*ft^-3. If the volume is constant then mounting the tank on load cells might give you a means for determining ice/water ratio.

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I agree that this is the best way to check it. We discussed this option but it isn't going to be possible due to the size of the tank.

I'm going to play with a laser distance sensor from IFM mounted in an acrylic box, but I'm afraid that it isn't going to be very consistent due to variation in the clarity of the ice.

It doesn't need to be too accurate, +- 5mm should give a good estimate of the capacity.

Right now the returning (warm) ice water temperature is measured and if it is above a setpoint then the return flow is diverted to another ammonia chiller pack (self contained ammonia system - compressor, condenser, phx, etc.) where it is pre-cooled to avoid depleting our ice. I want to know how much ice we have because we don't need to pre-cool if we have plenty of capacity -latent heat. Starting up the chiller pack uses a lot of energy, the condenser is gylcol cooled so there are a lot of pumps and fans to start up as well.

Just curious

steveb1475 said:

We discussed this option but it isn't going to be possible due to the size of the tank.

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How big is the tank? We measure silos several stories tall so I do not see how size could be an issue.

The size isn't the issue I guess, its the cost due to the size.

mellis said:

I don't think you will find an easy answer.

You could measure thickness of ice at one point with a radar or ultrasonic level transmitter possibly.

You could measure total quantity of ice by measuring the weight of the entire ice builder. Ice weighs less than water. Certainly not easy or cheap.

Click to expand...

mellis, do you have any suggestions for radar or ultrasonic transmitters?

steveb1475 said:

The size isn't the issue I guess, its the cost due to the size.

Click to expand...

OK. I was just curious because we do alot of weight based projects and I have never ran across one where we couldn't get load cells big enough.


IMHO weighing would be your best method since it would take the total ice weight in as a factor and you could also use this data to trend with if your trying to predict when your going to run out of cooling ability. This trending may need to figure into your cost analyst as well.

I can buy 40 ton load cells for less than 500 bucks and using Beckhoff KL3356 load cell modules I can read them over ethernet for about 250 bucks per channel. I'm trying to imagine your setup but unless it is incredibly massive I'm having a hard time seeing why it wouldn't be economically feasible.