Monday, April 27, 2015

Differences Between a Regenerative Turbine Pump and a Centrifugal Pump

Regenerative turbine pump have double row vanes cut in the rim. The impeller rotates within two liners into which annular channels have been milled. Liquid flows in at the suction and is picked up by the impeller vanes. In completing nearly one revolution in the annular channel, the fluid develops a high velocity and pressure increases dramatically before being sent out the discharge. The liquid re-circulates between the impeller vanes and the annular chamber. Because of this action, the fluid flows in a path like a helical spring laid into each of the annular grooves as the fluid is carried forward. Energy is added to the fluid by a number of vortex impulses in the impeller vanes, as it travels from suction to discharge.

These impulses have the same effect as multi- staging in a centrifugal pump. In a multistage centrifugal pump, the pressure is the result of energy added in each stage. In a turbine pump, pressure is added to the fluid stream by circulating many times through the vanes of a single impeller.



One of the most remarkable features of the regenerative turbine pump is its performance characteristics when pumping highly volatile liquids. The manner in which the turbine impeller imparts velocity/energy to the fluid, as described above, is quite different from conventional centrifugal or positive displacement designs. The continuous, progressive building of pressure in a regenerative turbine pump essentially eliminates the sudden collapse of bubbles that is destructive cavitation.

turbine pump can develop about ten times the discharge pressure of a centrifugal type having equal impeller diameter and speed. Pressure increases nearly uniformly around the impeller rim. At the impeller hub, the pressure is about one half the discharge pressure. This lower pressure, plus suction pressure, is what is seen in the stuffing box. Holes through the impeller keep the impeller centered to reduce wear, prevent unbalanced pressures on the impeller and reduce end thrust on the bearings.

REGENERATIVE PUMP DESIGN ADVANTAGES
  • Develop higher pressures
  • Can be run at lower motor speeds
  • Eliminate cavitation
  • Operate with lower NPSHr
  • Deliver specified capacity with input pressure variations
  • Meet performance with fewer stages
  • Smaller size
For more information on regenerative turbine pumps, contact:

Mountain States Engineering and Controls
1520 Iris Street
Lakewood, CO 80215
303.232.4100 Phone
303.232.4900 Fax
Email: info@mnteng.com

Tuesday, April 14, 2015

Wet Cooling Towers

Cooling tower (courtesy
of Delta Cooling Tower)
Water cooling towers are some of the most essential pieces of equipment for commercial and industrial buildings today.

Cooling towers may either use the evaporation of water to remove process heat to cool the process fluid, or may use forced or convective air to cool the process fluid.

Wet cooling towers use the natural process of evaporation (of water) to cool equipment.  They rely on an exchange of heat between the equipment, the water in the tower, and the air passing through the tower.

Excess process heat is absorbed by the water in the cooling tower as it passes through a labyrinth of fins and tubes in the structure. As the water is warmed, it comes into direct contact with cool air passing through the tower. The interaction between cool air and warm water causes the warmest water droplets to evaporate and is released out of the tower into the atmosphere. The remaining water cools back down and can be reused through the system again.

Common applications include cooling the circulating water used in refineries, chemical plants, power stations and HVAC systems for cooling buildings. Due to the cost-effectiveness and readily available supply of water, companies use wet cooling towers to provide cooling continuously and cheaply.

While cooling towers are normally defined as “a heat rejection device which rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature”,  one must keep in mind that the “waste heat” emissions are just water droplets, and are not harmful to the atmosphere nor to the environment.

Friday, April 10, 2015

Electrical Pressure Sensor Types

Here is an introduction to the basics of electrical pressure sensors, from Tony Kuphaldt's Lessons in Industrial Instrumentation.

This presentation explains how a variety of electrical pressure sensors work, including piezoresistive (strain gage), differential capacitance, and resonance sensors.

Sensor principles, sensor mounting and associated hardware design for pressure transmitters and differential pressure transmitters are also described.

Click on the image below to open the presentation (viewable on all devices).


pressure sensors
Click on image to see presentation.