For what industrial application will you recommend using peristaltic pump? For m

Question

For what industrial application will you recommend using peristaltic pump? For most cooling/heating applications, which type of heat exchanger (counter current or co-current) is commonly used and why? What is the main driving force in heat transfer process and the driving force in momentum transfer process? What causes cavitation process to take place when using a pump? A hot water at 80 degree C flow through an insulated tube of 50-mm outer diameter and it is 1 m long. The thickness of the insulation is 40 mm made of a material for which its thermal conductivity is 0.05 W/m. degree C. If the temperature of the outer surface of the insulation is 50 degree C, what is the rate at which heat is loss through the pipe? A municipal water supply system requires to supply water from the city's water reservoir at a rate of 10,000 cm^3/s to an elevated tank 200 m away and 50 m higher in altitude relative to the reservoir. The pipe line between the reservoir and the elevated tank is a 4-in schedule 40 cast iron pipe. The piping fittings consist of 4 90 degree elbows, 8 half open gate valves and 1 wide open globe valve. Calculate the power needed for the pump assuming that the pump efficiency is 70% and include both losses at the reservoir exit and the tank entrance.

Explanation / Answer

For What industrial applications will you recommend the Peristaltic pump ?

Peristaltic pump

A peristaltic pump is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a circular pump casing (though linear peristaltic pumps have been made). A rotor with a number of "rollers", "shoes", "wipers", or "lobes" attached to the external circumference of the rotor compresses the flexible tube. As the rotor turns, the part of the tube under compression is pinched closed (or "occludes") thus forcing the fluid to be pumped to move through the tube. Additionally, as the tube opens to its natural state after the passing of the cam ("restitution" or "resilience") fluid flow is induced to the pump. This process is called peristalsis and is used in many biological systems such as the gastrointestinal tract. Typically, there will be two or more rollers, or wipers, occluding the tube, trapping between them a body of fluid. The body of fluid is then transported, at ambient pressure, toward the pump outlet. Peristaltic pumps may run continuously, or they may be indexed through partial revolutions to deliver smaller amounts of fluid.

It used in variety off applications some of which are listed below.

·         Medicine

·         Dialysis machines

·         Open-heart bypass pump machines

·         Medical infusion pumps

·         Testing and research

·         AutoAnalyzer

·         Analytical chemistry experiments

·         Carbon monoxide monitors

·         Media dispensers

·         Agriculture

·         'Sapsucker' pumps to extract maple tree sap

·         Food manufacturing and sales

·         Liquid food fountains (ex. cheese sauce for nachos)

·         Beverage dispensing

·         Food-service Washing Machine fluid pump

·         Chemical handling

·         Printing, paint and pigments

·         Pharmaceutical production

·         Dosing systems for dishwasher and laundry chemicals

·         Engineering and manufacturing

·         Concrete pump

·         Pulp and paper plants

·         Minimum quantity lubrication

·         Water and Waste

·         Chemical treatment in water purification plant

·         Sewage sludge

·         Aquariums, particularly calcium reactors

2.For most of the cooling applications which type of heat exchanger is used and why?

Let's take the case when we want to extract the maximum amount of heat from a given hot stream. What design should we adopt? The figure below depicts heat exchanger schematics and the temperature profiles for both cocurrent (or parallel) and countercurrent designs:

Hence, in a cocurrent design, the temperature of the cold stream outlet, Tc,outTc,out is always lesser than that of the hot stream outlet, Th,outTh,out. Therefore, the heat transfer is restricted by the cold stream's outlet temperature, Tc,outTc,out.

On the other hand, in a countercurrent design, the restriction is relaxed and Tc,outTc,out can exceed Th,outTh,out. Hence in this design, the heat transfer is restricted by the cold stream's inlet temperature, Tc,inTc,in.

Therefore, to achieve greater heat recovery, a countercurrent design is preferred to that of a cocurrent design.

However, there are some special cases where a cocurrent exchanger design might still be adopted. Some of these are:

What is pump cavitation?

Simply defined, cavitation is the formation of bubbles or cavities in liquid, developed in areas of relatively low pressure around an impeller. The imploding or collapsing of these bubbles trigger intense shockwaves inside the pump, causing significant damage to the impeller and/or the pump housing.

If left untreated, pump cavitation can cause:

There are two types of pump cavitation: suction and discharge.

Suction Cavitation

When a pump is under low pressure or high vacuum conditions, suction cavitation occurs. The pump is being "starved" or is not receiving enough flow. When this happens, bubbles or cavities will form at the eye of the impeller. As the bubbles carry over to the discharge side of the pump, the fluid conditions change, compressing the bubble into liquid and causing it to implode against the face of the impeller.

An impeller that has fallen victim to suction cavitation will have large chunks or very small bits of material missing, causing it to look like a sponge.

Possible causes of suction cavitation:

Discharge Cavitation

When a pump's discharge pressure is extremely high, or runs at less than 10% of its best efficiency point (BEP), discharge cavitation occurs. The high discharge pressure makes it difficult for the fluid to flow out of the pump, so it circulates inside the pump. Liquid flows between the impeller and the housing at very high velocity, causing a vacuum at the housing wall and the formation of bubbles.

As with suction cavitation, the implosion of those bubbles trigger intense shockwaves, causing premature wear of the impeller tips and pump housing. In extreme, discharge cavitation can cause the impeller shaft to break.

Possible causes of discharge cavitation:

Cavitation Prevention

If your pumps are experiencing cavitation, check these things to troubleshoot the problem on your own:

For more information about how to detect and prevent pump cavitation, be sure to check out our post: Technologies To Detect and Prevent Pump Cavitation.

Cavitation is a common problem in pumping systems, but with proper pump sizing, pipe design, and care of filters and strainers, damage to pumps and their impellers can be largely avoided.

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