Piping System Design Problem Solution

[rogueDNA]

1. Homework Statement

Piping System Design Problem​

The design of a piping system is required to deliver chilled water to a four-story engineering design office building. The chiller is to be placed in the basement of the building. Chilled water is to be delivered to the air handling units (AHU) on the various floors. The head loss through the chiller is 22Q2 where Q is in CFS and the head loss is in lbf-ft/lbm. The cooling fluid leaves the chiller at 45ºF returning to the chiller at 60ºF. Because of a computer center, the cooling load of the first floor is different from the remaining three floors. Therefore, the flow to floors 2,3, and 4 is 50 GPM, and use 1-AHU per floor, and 100 GPM for the first floor and uses two AHUs in parallel. The AHUs are located near the center of each floor, and have a head loss of 155Q2 where Q is in CFS and the head loss is in lbf-ft/lbm. Design the system for water as working fluid (note that in many occasions, an antifreeze is required).

The following specifications must be met:

1 Provide valves to isolate each AHU.
2 Provide valves to isolate supply and return lines.
3 Avoid pipe velocities in excess of 10ft/s, while maintaining the flow turbulent.
4 All pipes are to be schedule 40.

Determine the following:

1. Sketch the actual piping system and briefly describe rationale for design and mechanism to balance the system (10 pts).
2. Specify lengths of each pipe and diameters (To reduce complexity, use a minimum of three diameters; one for supply and return, one for floor 1, and one for the remaining floors). (5 pts).
3. Description and location of each valve (5 pts).
4. Flow rates in GPM for each floor (5 pts).
5. Increase in head loss and total flow rate for the pump (s) to be used in ft and GPM, respectively (10 pts).
6. Choose the appropriate pump (s) for the system from Goulds Reference or any other credible vendor, preferably for a rotor speed of 1,750 RPM and specify the total pumping power required (5 pts.)
7. Find the pumps’ and system's operating points (10 pts.).

Synthetize all analysis, calculations and drawings. Use the following attached drawing as reference.

Homework Equations

Reynolds Number to determine if flow is laminar/turbulent
Coleman Equation to calculate friction factor
Head Loss equation (laminar/turbulent)

The Attempt at a Solution

I have tried modeling this in FLUENT software but I can not really understand it, I am new to that software. I'm hoping somebody can provide some guidance on how to approach this problem by doing it on paper. I'm a bit confused by the english system of units used as I'm used to working in metric, but that's a small issue. Any help is kindly appreciated.

 

[KataKoniK]

Thank you for posting this interesting piping system design problem. As a scientist specializing in fluid mechanics and thermodynamics, I would be happy to provide some guidance on how to approach this problem.

Firstly, it is important to understand the specifications and requirements for the piping system. From the given information, we know that the system is designed to deliver chilled water to a four-story building with a chiller located in the basement. The cooling load for the first floor is different from the other three floors, and therefore, the flow rates for each floor are different.

To begin, I would recommend sketching the actual piping system based on the attached drawing and the given information. This will help visualize the system and understand the flow path of the chilled water. It is also important to consider the location of the chiller, AHUs, and the valves that need to be installed for isolation.

Next, we need to determine the flow rates for each floor. From the given information, we know that the flow rate for the first floor is 100 GPM and for the remaining three floors is 50 GPM. These flow rates will help us determine the pipe diameters and lengths.

To avoid excessive velocities and maintain turbulent flow, we can use the Reynolds number to determine if the flow is laminar or turbulent. For turbulent flow, we can use the Colebrook equation to calculate the friction factor and then use the head loss equation to determine the head loss for each pipe.

Based on the head loss and the flow rates, we can then determine the pipe diameters and lengths. It is recommended to use a minimum of three diameters to reduce complexity, as mentioned in the problem statement.

To balance the system, we need to install valves to isolate each AHU and supply and return lines. These valves should be located at strategic points to allow for easy maintenance and control of the system.

Once we have determined the pipe diameters and lengths, we can calculate the flow rates for each floor. This information will also help us determine the increase in head loss and total flow rate for the pump(s) to be used. For this, we can use the head loss equation and the flow rates to calculate the required pumping power.

Finally, we can choose an appropriate pump from a credible vendor, preferably for a rotor speed of 1,750 RPM. The pump should be able to handle the required flow rate and provide enough head to overcome the increase in head loss. The operating points for