Showing posts with label differential flow. Show all posts
Showing posts with label differential flow. Show all posts

Friday, February 16, 2018

Campus Metering: Advantages of Using V-Cone for Measuring Chilled Water & Steam in Hospitals, Universities, and Institutions

McCrometer's V-Cone
Typical diagram of V-Cone installation.
(Click for larger view).
McCrometer's V-Cone® Flow Meter is an advanced differential pressure instrument, which is ideal for use with liquid, steam or gas media in rugged conditions where accuracy, low maintenance and cost are important. The V-Cone is especially useful in tight-fit and retrofit installations. 

In most instances the use of V-Cones associated with chillers for chilled water in large institutional users is a matter of space, accuracy, and turndown. The V-Cone needs very little upstream and downstream piping requirements, allowing it to be used in spaces where other meters cannot be used, or to replace existing flowmeters that never proved accurate because of space limitations. 

In many large universities and other facilities, such as hospitals and airports, across the U.S., the reason for initial interest and subsequent purchases of V-Cones to measure Chilled Water was to fit within the confines of the existing and new buildings that were being used to house the chillers. Additionally, the second most important reason was the delivered accuracy. In the past, most usage had been ignored, but with the rising costs associated with cooling, each individual building must be accountable for individual use. This is just good fiscal responsibility and management from an energy balance standpoint. Turndown was an issue because of seasonal swings in usage based on climate and population in the buildings at any particular time. Therefore, the meters needed to be able to have a large flow span (turndown), which remained accurate during continuous use.
McCrometer's V-Cone
Internal view of V-Cone.

V-Cones have recently been selected for Steam service for mostly the same reasons as they are selected for Chilled Water. Space limitations in new and/or older buildings are a serious concern. V-Cones have the smallest piping requirements of practically any flowmeter and continue to deliver accurate measurement, so they are fiscally responsible and cost effective. Additionally, in steam, they allow condensate and/or other small particulate matter to pass without affecting the measurement, thus giving much better accuracy instantaneously and over time. 

They are very rugged flowmeters which require little or no maintenance, and have a very long expected life even in “tough” service like steam. They can be designed with great turndown (span) and therefore can accommodate changes in flowrates based on demand, seasonal or from other factors.

For more information on V-Cone flowmeters, contact Flow-Tech in Maryland at 410-666-3200, in Virginia at 804-752-3450, or by visiting

Thursday, November 30, 2017

Differential Flowmeters: How They Work

Differential Flowmeters
The differential flow meter is the most common device for measuring fluid flow through pipes. Flow rates and pressure differential of fluids, such as gases vapors and liquids, are explored using the orifice plate flow meter in the video below.

The differential flow meter, whether Venturi tube, flow nozzle, or orifice plate style, is an in line instrument that is installed between two pipe flanges.

The orifice plate flow meter is comprised the circular metal disc with a specific hole diameter that reduces the fluid flow in the pipe. Pressure taps are added on each side at the orifice plate to measure the pressure differential.

According to the Laws of Conservation of Energy, the fluid entering the pipe must equal the mass leaving the pipe during the same period of time. The velocity of the fluid leaving the orifice is greater than the velocity of the fluid entering the orifice. Applying Bernoulli's Principle, the increased fluid velocity results in a decrease in pressure.

As the fluid flow rate increases through the pipe, back pressure on the incoming side increases due to the restriction of flow created by the orifice plate.

The pressure of the fluid at the downstream side at the orifice plate is less than the incoming side due to the accelerated flow.

With a known differential pressure and velocity of the fluid, the volume metric flow rate can be determined. The flow rate “Q”, of a fluid through an orifice plate increases in proportion to the square root the pressure difference on each side multiplied by the K factor. For example if the differential pressure increases by 14 PSI with the K factor of one, the flow rate is increased by 3.74.