Design Review #1 (Aug 25th 2014 - Oct 28th 2014)
1. Introduction
SPX manufactures cooling towers and sound attenuation for all kinds of settings. Many of these cooling towers are located in areas where excess sound is a major problem. The current sound attenuation used by SPX has limitations that they believe can be improved upon. The main factors that are considered when dealing with sound attenuation are insertion loss, pressure drop, and cost of manufacturing.
Testing insertion loss is the key to designing any sound attenuator. Due to the importance of this testing, ATC-128 test code was developed by the Cooling Technology Institute to standardize insertion loss testing. In order to make any improvements to current attenuation designs, proper testing must be done to measure the effectiveness of the attenuation.
SPX is in a need of an improved sound attenuation design that will improve upon the current insertion loss while not having an adverse effect on pressure drop or cost.
Testing insertion loss is the key to designing any sound attenuator. Due to the importance of this testing, ATC-128 test code was developed by the Cooling Technology Institute to standardize insertion loss testing. In order to make any improvements to current attenuation designs, proper testing must be done to measure the effectiveness of the attenuation.
SPX is in a need of an improved sound attenuation design that will improve upon the current insertion loss while not having an adverse effect on pressure drop or cost.
2. Problem Statement
The current design of SPX sound attenuators is effective and easy to replicate. The design consists of rectangular baffles spaced evenly with the attenuator with the baffles being constructed of perforated metal filled with sound absorption material. While this design is effective, SPX believes that improvements can be made to increase effectiveness. New attenuator designs could bring greater insertion loss for the same current cost. SPX gave our design team the task of helping to formulate these new designs.
Certain constraints need to be considered when formulating new designs. First and foremost the new design must be able to attach to current SPX cooling towers. A design that does not attach to the cooling tower would be useless. Another constraint is that the pressure drop and airflow impedance must be considered. A design that does not allow enough airflow or reduces the flow pressure too drastically will not allow the cooling tower to be effective. Cost of manufacturing and production must also be considered when thinking of new designs. The new design needs to be cost efficient in order for the new design to be an improvement over current attenuation.
Our group and SPX have come to an agreement on the design goals for this project. The main goal is to design and alternative cooling tower sound attenuation setup that increasing sound attenuation while improving or holding constant cost and thermal performance. A more quantitative goal that we have agreed on is the design will decrease sound by 3dB and/or decrease cost by 30% and/or decrease pressure drop by 30%. These benchmarks will be used to determine the success of the new designs that our group creates. The last goal deals with timeline and the goal is that our design(s) will be completed and sent to SPX before May 2015 due to the design group graduating from Kansas State at that time.
Our group is excited to improve sound attenuation on SPX cooling towers. We will deliver SPX all the drawings, calculations, and other documents necessary to use the improved design in the field. The project timeline will unfold in a manner described by the Gantt chart below.
Certain constraints need to be considered when formulating new designs. First and foremost the new design must be able to attach to current SPX cooling towers. A design that does not attach to the cooling tower would be useless. Another constraint is that the pressure drop and airflow impedance must be considered. A design that does not allow enough airflow or reduces the flow pressure too drastically will not allow the cooling tower to be effective. Cost of manufacturing and production must also be considered when thinking of new designs. The new design needs to be cost efficient in order for the new design to be an improvement over current attenuation.
Our group and SPX have come to an agreement on the design goals for this project. The main goal is to design and alternative cooling tower sound attenuation setup that increasing sound attenuation while improving or holding constant cost and thermal performance. A more quantitative goal that we have agreed on is the design will decrease sound by 3dB and/or decrease cost by 30% and/or decrease pressure drop by 30%. These benchmarks will be used to determine the success of the new designs that our group creates. The last goal deals with timeline and the goal is that our design(s) will be completed and sent to SPX before May 2015 due to the design group graduating from Kansas State at that time.
Our group is excited to improve sound attenuation on SPX cooling towers. We will deliver SPX all the drawings, calculations, and other documents necessary to use the improved design in the field. The project timeline will unfold in a manner described by the Gantt chart below.
3. Design of Experiments
Our group decided the best way to find the most important design considerations was to perform a design of experiments. We believe this experiment will help us to find the most important aspects of the attenuator design and make it easier to make an effective design.
We decided two separate design of experiments were necessary in order to test both of our baffle geometries and get an accurate conclusion. The two main geometries we are considering are rectangular baffles (similar to current set-up) and cylindrical baffles. The first table below details the design of experiments for the rectangular baffles. The three variables we chose to test in the experiment were surface area, angle (of contact), and number of baffles. The second table below shows our table for the cylindrical baffles. The three variables we chose for this experiment were diameter, horizontal shift, and number of baffles.
We decided two separate design of experiments were necessary in order to test both of our baffle geometries and get an accurate conclusion. The two main geometries we are considering are rectangular baffles (similar to current set-up) and cylindrical baffles. The first table below details the design of experiments for the rectangular baffles. The three variables we chose to test in the experiment were surface area, angle (of contact), and number of baffles. The second table below shows our table for the cylindrical baffles. The three variables we chose for this experiment were diameter, horizontal shift, and number of baffles.
4. Proposed Test Set-Up
![Picture](/uploads/2/5/3/2/25322222/9791698.png?424)
Purpose: To obtain sound measurements to compare different attenuator configurations.
Materials:
· 20’ Box Fan
· Sound Measuring Device
· 2’ x 2’ x 2’ Attenuator Housing
· Scaled Attenuators
· Plywood Containment
· Insulation material
Procedure:
1. Testing unit will be set up as shown below with first configuration.
2. Turn on fan
3. Measure decibel level on the inlet side of the attenuator housing through measuring port.
4. Measure decibel level on the outlet side of the attenuator housing at the following areas:
a. Outlet measuring port
b. Directly horizontal from outlet at 1 foot and 5 feet
c. Directly vertical from outlet at 1 foot and 5 feet
5. Repeat with next configuration till design of experiment is completed.
Materials:
· 20’ Box Fan
· Sound Measuring Device
· 2’ x 2’ x 2’ Attenuator Housing
· Scaled Attenuators
· Plywood Containment
· Insulation material
Procedure:
1. Testing unit will be set up as shown below with first configuration.
2. Turn on fan
3. Measure decibel level on the inlet side of the attenuator housing through measuring port.
4. Measure decibel level on the outlet side of the attenuator housing at the following areas:
a. Outlet measuring port
b. Directly horizontal from outlet at 1 foot and 5 feet
c. Directly vertical from outlet at 1 foot and 5 feet
5. Repeat with next configuration till design of experiment is completed.
![Picture](/uploads/2/5/3/2/25322222/6873124.png?105)
4.1. Possible Sound Measuring Devices
For this test procedure to work, we need to have a reliable sound meter to measure decibel readings. Currently we are looking at two different options that are produced and sold by McMaster-Carr. The two meters we are looking at are the 40 to 130 dB Meter and the 35 to 130 dB Meter. Both of these monitors have selectable A and C scales to adjust the frequency response. The A scale is similar to the response of the human ear and is used by OSHA. The C scale is suitable for measuring the sound level of machinery. We are looking at the monitors with NIST certificate included which means the monitor will come with a calibration certificate traceable to the National Institute of Standards and Technology.
For this test procedure to work, we need to have a reliable sound meter to measure decibel readings. Currently we are looking at two different options that are produced and sold by McMaster-Carr. The two meters we are looking at are the 40 to 130 dB Meter and the 35 to 130 dB Meter. Both of these monitors have selectable A and C scales to adjust the frequency response. The A scale is similar to the response of the human ear and is used by OSHA. The C scale is suitable for measuring the sound level of machinery. We are looking at the monitors with NIST certificate included which means the monitor will come with a calibration certificate traceable to the National Institute of Standards and Technology.
![Picture](/uploads/2/5/3/2/25322222/5484401_orig.png)
4.2. Possible Manometer for Pressure Drop Calculation
In addition to an accurate sound measuring device, we will also need a manometer to help us determine pressure drop through the attenuator. The current manometer we are looking at is the PYLE Meters PDMM01 Digital Manometer with 11 units of measure. This manometer has an accuracy of +/- 0.3% which will be adequate for the relative readings we will be measuring from our test set-up. Below is a picture of our proposed manometer.