Chilled water loop pressure and velocity

In summary, the conversation revolves around investigating the possible causes of a rooftop unit that is not performing as it should. The variables mentioned include the pipe size, flow rate, and pipe length. The pressure in the pipe can be determined with these given variables, but the length of the pipe indirectly affects the velocity. The pressure drop is mainly caused by friction on the inside of the pipe and losses due to viscous forces within the liquid.
  • #1
tmerc
5
0
Where i work has a chilled water loop to every building for the ac system. A rooftop unit has not been performing as it should so we are investigating into the possible causes. Right now i am trying to come up with the different variables that accompany the givens. I know the pipe is 2.5", the flow rate must have been measured at some point because one of the drawings says 53 GPM, and the length of the pipe is approximately 135'. Now is there any way to determine the pressure in the pipe with these givens. And also, would the length of the pipe effect the velocity or is that just based off the flow rate and diameter?
 
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  • #2
You can determine the pressure drop through that length of pipe, but that's about it.

The length of pipe affects the velocity indirectly. As the length of pipe affects the pressure drop, it in turn affects the flow rate, which in turn determines (along with pipe diameter) the flow velocity.
 
  • #3
Correct me if i am wrong, the pressure drop is causes by the friction on the inside of the pipe?
 
  • #4
tmerc said:
Correct me if i am wrong, the pressure drop is causes by the friction on the inside of the pipe?

Yep, pipe friction and losses due to viscous forces within the liquid itself (turbulence and all that), chiefly.
 
  • #5


I would approach this issue by first understanding the basics of fluid dynamics and how they apply to chilled water systems. In this case, the chilled water loop is essentially a closed system with a fixed flow rate, pipe diameter, and length. The pressure and velocity of the water within the loop are directly related to each other and can be calculated using the Bernoulli equation.

Based on the information provided, we can assume that the flow rate of 53 GPM and the pipe diameter of 2.5" are constant. The length of the pipe, however, can have an effect on the pressure and velocity of the water. This is because the longer the pipe, the more friction and resistance the water will encounter, resulting in a decrease in velocity and an increase in pressure.

To determine the pressure within the pipe, we would need to know additional variables such as the elevation and the type of pipe material. These factors can affect the pressure and would need to be considered in the calculations.

In terms of the velocity, it is primarily determined by the flow rate and pipe diameter. However, the length of the pipe can also have a small effect on the velocity due to friction. This can be calculated using the Darcy-Weisbach equation, which takes into account the pipe length, diameter, and roughness.

In conclusion, while the given information provides a good starting point for investigating the issue with the rooftop unit, additional variables and calculations would be needed to accurately determine the pressure and velocity within the chilled water loop. As a scientist, it is important to consider all factors and use mathematical equations to analyze and solve problems in a systematic and accurate manner.
 

1. What is a chilled water loop pressure and velocity?

A chilled water loop pressure and velocity refers to the pressure and speed at which water flows through a closed loop system used to cool buildings and other structures. This system typically consists of a chiller, pumps, and piping to circulate chilled water throughout the building, absorbing heat and maintaining a comfortable temperature.

2. How does chilled water loop pressure and velocity affect energy efficiency?

The pressure and velocity of water in a chilled water loop can greatly impact the energy efficiency of the system. Higher pressure and velocity can result in increased energy consumption and wear on equipment, while lower pressure and velocity can lead to reduced cooling efficiency. It is important to carefully balance the pressure and velocity to optimize energy efficiency.

3. What is the recommended pressure and velocity for a chilled water loop?

The recommended pressure and velocity for a chilled water loop can vary depending on the specific system and building needs. However, in general, the pressure should be between 10-15 psi and the velocity should be between 3-5 feet per second. It is important to consult with a professional to determine the best pressure and velocity for your specific system.

4. How can I monitor and adjust the pressure and velocity in my chilled water loop?

There are various instruments and tools available to monitor and adjust the pressure and velocity in a chilled water loop. These include pressure gauges, flow meters, and control valves. Regular maintenance and monitoring are key to ensuring optimal pressure and velocity for energy efficiency and system performance.

5. What are the potential problems associated with incorrect chilled water loop pressure and velocity?

If the pressure and velocity in a chilled water loop are not properly balanced, it can result in a range of problems. These may include reduced cooling efficiency, increased energy consumption, equipment wear and tear, and potential system failures. It is important to regularly monitor and adjust the pressure and velocity to avoid these issues and maintain optimal system performance.

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