OIL COOLING SYSTEMS

What utilities do you have available to cool the oil? City water? Or, do you want to reject the heat to the ambient air?

Yes, there is city water available. I am not sure, but I think there is some condenser water available, so heat rejected to an outside tower might be a possibility. Even if I use city water, I would have to design a remote heat exchanger to dump the heat.

I already designed an air cooling system but it was rejected because the ventilation system in the machine room was inadequate. Most of the heat realease goes into the oil and the room and this is part of the problem that I am trying to address.

Is there a Schematic for the elevator with component part numbers and a Sequence of operation?

All heat in a hydraulic circuit is produced by wasted energy and can usually be designed out of the circuit quite easily. Especially a circuit like the one you described.

As for a cooling system, a simple way would be to immerse some coiled tubing into the 750 gallon tanks and use a thermostaically controlled water valve to turn water flow on to thecoils at 120 Deg.F. and off at 100 Deg.F.

Another option is to use some 20W50 Engine oil that operates very well at 180 Deg.F.

what is 2050mw oil?

I made some control computations and based on the values you gave it is necessary to evacuate about 9kW (thermal energy) in order to maintain the temperature at the level you aim at. This in the case of a continuous cooling during the day. If you accept that during the day the temperature can reach the 180°F and cooling will be only during night you can reduce the cooling power but not too much.

You idea of using a coil in the reservoir presents some negative aspects (only from the heat transfer point of view) oil has a lower heat transfer coefficient than water which leads in usual heat exchanger to put the fluid with the lower coef. in the tubes ans let it flow at higher speeds and the fluid with the higher coef. at the outside circulating at lower speeds-in this case water.

If you put a coil in the reservoir you are confronted with:

-contact with oil you will have a free convection with a low coef. and it will require a big transfer area.

- you can correct it partially with finns but there is a risk of dirt deposit (reduction of heat transfer over time) and of disturbing oil circulation in the reservoir.

It would be better to use an external heat exchanger with an oil circulation (low pressure pump) and with water as transport fluid in order to obtain smaller dimensions. The hot water flow can be used for other goals or air cooled and recirculated (which would be better in order to reduce the risk of deposits due to mineral content of water which also reduces the heat transfer over time).

Temperature monitoring can limit the power consumption.

For the week end you can reduce the cooling power since the time to evacuate the heat is 4x longer (48 h versus 12). However a reserve must be considered in all cases.

I hope it will help.

This is one of the paths that I would like to follow for the design. I am actually doing the schematics right now. Here are a few of my concerns.

How would you address the leveling problem in the 2 tanks. If I draw oil from the resovior to cool it, that would cause an imbalance between the two tanks? Would that affect the operation of the system.

what precautions do you suggest I take to prevent any water leakages in the heat exchanger and the room.

Is this problem on an existing unit?

In most hydraulic systems the surface area of the tanks is used to dissipate the heat. Is the oil not being drawn through both tanks? Drawn from one and returned to the other. Is the level of both tanks correct. Incorrectly adjusted relief valve could cause over heating of fluid. To high of viscosity fluid can cause over heating.

I am far from a guru of any sort but will offer a few reflections.

Is this equipment in an enclosed space without ventilation? If so, I see that as a primary problem that will over-tax whatever cooling system you decide on. You have the system losses to remove, but also anything else in the room like the motor driving the pump. I would start with an air supply/exhaust system (even better if A/C) that will keep the room purged at all times and would shut down based on oil temp or ambient temp.

Rather than using city water which would be quite wasteful, you can add a chill water closed loop cooling system to the system which could be regulated to give you any oil temp you desire and cycle on and off with demand. The oil can be cooled in tubed or plated heat exchangers. I would suggest that the system tank (return) and pump case drain lines be cooled as they are the source of heat to the reservoir; they should be cooled separately as not to add back pressure from the return line to the case drain. I would still see a need to cool or ventilate the room; significantly more if the chiller unit is in the same space and somewhat less if it is remote.

Fast Solution at low investment:

Install a closed circuit water( any clean potable tap water to start with) loop with a 1/2HP monoblock centrifugal domestic-use water pump . This will develope say 1Kg/cm2 outlet pressure when you pass the water through a chilling water Copper tube coil TC with tube 10x1mm -surface 1sq mtr which will be inserted into the 750Gallon Service Hydraulic Oil day tank DT. The water carrying some heat out of the DT will now be dumped to an atmospheric(vented) tank from where the pump will also recirculate. This vented tank VT will be float-level maintained to a set level +/- 50mm from City water line.The Pump can operate from Thermostat at bottom of DT.

Deep Into VT insert the chilling fluid radiator of a 1 Ton split Unit LG or similar window airconditioner. AC unit can be operated from a thermostat in VT

Your oil cooling project will run quiet and cool -day/night--workingday/holiday.

-------------------

IF Air Venting is Possible near enough :You can insert AC Unit's Finned Tube Chiller directly to bottom of DT and eliminate the water loop altogether.

mm

I believe I am correct in assuming you have at least one water cooling or heat extraction system operating in your facility?

If so,

It would be to your best interest to look at a simple Shell and Tube heat exchanger. Use your existing circuit to remove the heat from the hydraulic circuit with very little effort.

Your elevator hydraulic circuit BTU's will be nothing as compared to facility air chilling and I'm almost sure there is room in the equation to facilitate this.

The link bellow may help you size an appropriate unit.

http://www.thermo-dynamics.com/pdfiles/sizing_guides/hx_sizing_guide.pdf

What I have done in similar cases with CNC machines is that we install a 5 ton condenser (the same kind we use for air conditioning) and instal a copper coil and an EV (expansion valve) in the oil tanks, you will be able to control the temperature just setting a termostate. It is very simple and with low cost. All the system must not excede $ 1200 usd. With the info you sent you need a 3 ton condenser but the price for 5 tons is very close so I suggest you to instal the 5 ton condenser.

Enrique Torres.

Dear Sir,

Y cant u go for a continuos cooling of the system, throu water circulation. So that u can maintain the oil viscosity within its fluctuating limit.