Back to Basics: What Makes a Good Pump?

Everyone is familiar with pumps, but how many people really think about how much depends on this ubiquitous invention? The scope of pump applications is wide: distribution and circulation of water in water supply and heat supply systems, irrigation in agriculture, in the oil industry, in fire extinguishing systems, etc.

A pump is a hydraulic machine designed to move fluid and impart energy to it. A schematic diagram of a simple pumping unit is presented below.

Figure 1 Pumping Unit Diagram
Figure 1: Pumping Unit Diagram
1 – intake valve; 2 – suction pipeline; 3 – vacuum gauge; 4 – pump; 5 – manometer; 6 – check valve; 7 – gate valve; 8 – pressure pipeline

Positive Displacement and Dynamic Pumps

According to the principle of operation, pumps can be divided into two main groups: positive displacement and dynamic. In positive displacement pumps, a certain volume of the pumped liquid is cut off and moved from the inlet to the pressure head, where additional energy is supplied to it. In pumps with dynamic action, the increase in energy occurs due to the interaction of the liquid with a rotating working body.

The most widely used pumps are centrifugal pumps which are of the dynamic type. The principle of centrifugal pumps uses a rotating impeller to create a vacuum in order to move the fluid. The impeller rotates within the housing and reduces pressure at the inlet. This motion then drives fluid to the outside of the pump’s housing, which increases the pressure.

These pumps benefit from a simple design and lower maintenance requirements and costs. This makes them suited to applications where the pump is used often or continuously run.

Figure 2 Centrifugal Pump
Figure 2a: Centrifugal Pump
Centrifugal Pump Designed using AxSTREAM
Figure 2b: Centrifugal Pump Designed using AxSTREAM

In most cases, the pumps are electrically driven, but if the pump is of high power and high speed, then these pumps are driven by steam turbines. Read More

Pump Rotor Dynamics – from Residential Pools and Human Hearts to Heavy Duty Industry Applications

You rarely find a rotary machine with a wider range of applications than pumps. These machines acting in a single role can be installed both to supply the water to a garden pool and move the crude oil in pipelines.

And even more, the same simple pump can substitute the functions of the human heart by moving the blood through it.

Fig. 1 - Left ventricular assist device - a tiny pump moving the blood in the human body
Fig. 1 – Left ventricular assist device – a tiny pump moving the blood in the human body [1]
Although the heavy duty industry applications of pumps are less delicate at first sight, they can still generate similar effects of this unique nature which is inherent only to this type of machine and should be studied carefully when executing rotor dynamics calculations. Read More

Modeling a Ground Source Heat Pump

Ground source heat pumps (GSHP) are one of the fastest growing applications of renewable energy in the world, with annual increase of 10% in about 30 countries over the past 15 years.  Its main advantage is that it uses normal ground or ground water temperatures to provide heating, cooling and domestic hot water for residential and commercial buildings. GSHP’s are proving to be one of the most reliable and cost-effective heating/cooling systems that are currently available on the market and have the potential of becoming the heating system of choice to many future consumers, because of its capacity for providing a variety of services such as heat generation, hot water, humidity control, and air cooling. Additionally,  they have the potential to reduce primary energy consumption, and subsequently provide lower carbon emissions, as well as operate more quietly and have a longer life span than traditional HVAC systems. The costs associated with GSHP systems are gradually decreasing every year due to successive technological improvements, which makes them more appealing to new consumers.

The basic purpose of a GSHP is to transfer heat from the ground (or a body of water) to the inside of a building. The heat pump’s process can be reversed, in which case it will extract heat from the building and release it into the ground. Thus, the ground is the main heat source and sink. During winter, the ground will provide the heat whereas in the summer it will absorb the heat.

A GSHP comes in two basic configurations: ground-coupled (closed-loop) and groundwater (open loop) systems, which are installed horizontally and vertically, or in wells and lakes. The type chosen depends upon various factors such as the soil and rock type at the installation, the heating and cooling load required, the land available as well as the availability of a water well, or the feasibility of creating one. Figure 1 shows the diagrams of these systems.

Two Basic Configurations
Figure 1. Two Basic Configurations of GSHP Systems. SOURCE: [1]
In the ground-coupled system (Figure 1a), a closed loop of pipe, placed either horizontally (1 to 2 m deep) or vertically (50 to 100 m deep), is placed in the ground and a water-antifreeze solution is circulated through the plastic pipes to either collect heat from the ground in the winter or reject heat to the ground in the summer. The open loop system (Figure 1b), runs groundwater or lake water directly in the heat exchanger and then discharges it into another well, stream, lake, or on the ground depending upon local laws. Between the two, ground-coupled (closed loop) GSHP’s are more popular because they are very adaptable.
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Unsteady Flow Simulation in Hydraulic Systems

An unsteady flow is one where the parameters change with respect to time. In general, any liquid flow is unsteady. But if a hydraulic system is working at constant boundary conditions, then the parameters of the fluid flow change slowly; thus this flow is considered steady. At the same time, if the parameters of the fluid flow oscillate over time relative to some constant value, then it called quasi-steady flow 1.

In practice, most fluid flows are steady or quasi-steady. Examples of the three flows are presented in Figure 1. Steady flow is presented by a simple pipe. The quasi-steady flow is represented by a sharpened edge channel. The unsteady flow is presented by an outflow from a reservoir.

Figure 1 - Different Types of Fluid Flow
Figure 1 – Different Types of Fluid Flow
Different Cases of Unsteady Flow

During operations, hydraulic systems act for long intervals at steady conditions which are called operating modes. Change between two different operating modes occurs over a short time interval (called a transient mode). If any hydraulic system works more than 95% of the time at these operating modes though, why is the unsteady flow is so important? Because the loads depend on time intervals. If the load is less, then the maximum system pressure is higher. Read More

An Introduction to Centrifugal Pumps

In every modern cleaning system there exists at least one pumping unit. With this in mind, understanding how it works and how to use it efficiently is critical to the successful operation and maintenance of that cleaning system. This blog will discuss centrifugal pumps in this context and take a look at important attributes to bear in mind when working with these systems.

In general, pumps are devices which impart energy to a flow of liquid.  Although there are different types of pumps based on the flow direction, blade designs, and so on, centrifugal pumps are in the majority of those used in cleaning systems.  Centrifugal pumps are simple, efficient, reliable, relatively inexpensive, and easily meet the needs of most cleaning system requirements including spraying, overflow sparging, filtration, turbulation and the basic function of moving liquids from one place to another using pressure.

A centrifugal pump uses a combination of angular velocity and centrifugal force to pump liquids.  The below figure illustrates the working principle of the centrifugal pump.

Centrifugal Pump

The pump consists of a circular pump housing which is usually made up of metals, (stain steels etc.) solid plastic, or ceramics.  The outlet extends tangentially from the diameter of the pump housing.  Inside the pump housing there is a rotating component an “impeller” which rotates perpendicular to the central axis and is driven by a shaft secured to its center of rotation.  The shaft, powered by an electric motor, enters the pump housing through a liquid tight seal which prevents leaking.  Liquid entering the pump through the inlet is swirled in a circular motion and displaced from the rotation center of the impeller by centrifugal force.  The combination of the swirling action (angular velocity) and centrifugal force (radial velocity) pushes the liquid out of the pump through the outlet.

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Upcoming Webinar: Design and Optimization of Axial and Mixed Flow Fans for High Efficiency and Low Noise

Thursday, May 18 | 10:00 – 11:00 AM EST

Axial Fan CAD Image
Registration is now open for our May webinar demonstrating best practices for the development of competitive, high efficiency, and low noise axial and mixed flow fans for different aerodynamic loadings.

Axial and mixed flow fans have been in high demand for a number of years. The application of these machines span many different industries including HVAC, automotive, appliance, military equipment, and much more. Like many other types of turbomachinery, changing industry standards and market trends have resulted in fierce rivalry to compete on lifespan, efficiency, environmental and user friendliness, and overall quality. With this in mind, it goes without saying that companies are looking for tools needed to develop highly efficient equipment while minimizing noise as quiet fans are typically more desirable which results in higher demand and marketability.

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