Tech Challenge

Tech Challenge

Feeding Chilled Water to a Laser

Stephen from UltraGold Microscopy is looking for a circulating chiller to provide at least 1000 W cooling at 0ºC. Most importantly, he needs the chiller to overcome 50 feet of head. The laser that the chilled water is fed to is located three floors above the room in which the chiller is kept. The lab has had a problem with burning out the pump on their current chiller (PolyScience® Temperature-Controlled Recirculator, 12910-16) and it provides little to no flow with such a head height. Their laser is a very expensive piece of equipment, and they cannot afford for it be damaged by overheating.

What would you suggest?

A. Purchase the PolyScience® Temperature-Controlled Recirculator (12930-78) chiller instead since it has a built-in turbine pump.

B. Purchase a new PolyScience® Temperature-Controlled Recirculator (12910-16) chiller, but add the Regenerative Turbine Pump (75588-20) to act as a booster pump to get the flow rate up and increase head height of the system to its maximum.

C. Purchase the Magnetic Drive Regenerative Turbine Pump (75588-10) and replace the internal pump to their existing chiller.

D. Change the internal pump again, but switch to a larger tubing to decrease back pressure placed on the bath’s integral pump.

Answers:

A. Purchase the PolyScience® Temperature-Controlled Recirculator (12930-78) chiller instead since it has a built-in turbine pump.

Incorrect. Although this chiller comes with a turbine pump built in, there are less expensive solutions. This option would have been sufficient from the start though!

B. Purchase a new PolyScience® Temperature-Controlled Recirculator (12910-16) chiller, but add the Regenerative Turbine Pump (75588-20) to act as a booster pump to get the flow rate up and increase head height of the system to its maximum.

Incorrect. They already have the chiller and know how to replace the internal pump, so they would not need to purchase an entirely new system. Additionally, the flow of this pump is higher than what the 12910-16 chiller can provide. If the chiller cannot provide the needed flow rate it will cause cavitation in the turbine pump, which would eventually fail as well.

C. Purchase the Magnetic Drive Regenerative Turbine Pump (75588-10) and replace the internal pump to their existing chiller.

Correct. They have already changed the internal pump twice, so they should be familiar with the process and the cost for the pump is far less than a new unit. With the assistance of the 75588-10 pump acting as a “booster,” the system will easily overcome the 50 feet of head and flow should be adequate. To further avoid cavitation or harming the booster pump when starting the system, they will need to ensure that they start the bath first and then start the booster pump. Inversely, when shutting down the bath they must shut down the booster pump first, then the bath.

D. Change the internal pump again, but switch to a larger tubing to decrease back pressure placed on the bath’s integral pump.

Incorrect. In this case, switching to a larger inner diameter tubing would not overcome a 50-foot head height. The magnetic drive pump in their current unit is intended for high flow low pressure applications; once the head height is taken into account, the pressure it puts the bath under is too great.

.

Calibrating Sensors

Charles Orwell at Calibration Origins would like to mix carbon monoxide (CO) gas into nitrogen (N) at a ratio of 0.5 to 2 liters per minute to accurately calibrate his customer’s sensors. He needs to measure the gases being mixed at an accuracy of 5% or better.

Which flowmeters would you suggest he use to mix his pure gases?

A. Cole-Parmer® Mass Flow Controllers for CO flow and N flow, then just the tubing and tubing connections to join the two lines to have the combined flow.

B. Cole-Parmer® Mass Flow Controllers for CO flow, and N flow. Then add a valve for each line to adjust the flow rates, tubing, and tubing connections to join the lines for a combined flow.

C. Cole-Parmer® Flowmeter System with a Multitube Frame and flow tubes for CO and N with two valve cartridges added to the frame to control flow. Then just the tubing and tubing connections join the two lines to have the combined flow.

D. Cole-Parmer® Flowmeter System with a Gas Proportioner Multitube Frame and flow tubes for CO measurement and nitrogen, then inlet and outlet adapters and tubing.

Answers:

A. Cole-Parmer® Mass Flow Controllers for CO flow and N flow, then just the tubing and tubing connections to join the two lines to have the combined flow.

Incorrect. This would work, as the meter can be set to control gas flow rates for either CO or N, however, it is a very expensive solution. The accuracy is very high at ±0.8%, and the user just needs ±5% or better.

B. Cole-Parmer® Mass Flow Controllers for CO flow, and N flow. Then add a valve for each line to adjust the flow rates, tubing, and tubing connections to join the lines for a combined flow.

Incorrect. Although these mass flowmeters are less expensive then the mass flow controllers in answer A, this is still a very accurate and expensive route for the user’s needs and specifications.

C. Cole-Parmer® Flowmeter System with a Multitube Frame and flow tubes for CO and N with two valve cartridges added to the frame to control flow. Then just the tubing and tubing connections join the two lines to have the combined flow.

Incorrect. Although we are now in the correct accuracy range for the user, he or she would not get 5% accuracy with this direct reading tube for carbon dioxide (CO₂) when trying to read carbon monoxide (CO) flow. Additionally there are other possible frames that will combine the gases without having to create such thorough tubing connections.

D. Cole-Parmer® Flowmeter System with a Gas Proportioner Multitube Frame and flow tubes for CO measurement and nitrogen, then inlet and outlet adapters and tubing.

Correct. We can calculate and create a correlation chart for CO flow in reference to the mm markings on the CO flow tube. For example 150 mm = 39.4 mL/min and 10 mm = 1.94 mL/min, which will meet the user’s needs, including accuracy, and even has the mixing tube built in. No need to worry about additional plumbing, fittings, and tubing!