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Performance Table Reader

Run the Performance Table Reader MicroSim Fullscreen

This sketch is built on the FanPedia MicroSim kit. To run it in the p5.js editor, add the ../shared-libs/ files it loads (fanpedia-sim.css, fanpedia-core.js, fanpedia-p5.js), or their published URLs, to the editor's index.html before pasting ch26-performance-table-reader.js.

About This MicroSim

The grid is the RBA 913 excerpt from Twin City Fan Catalog 902 (November 2017), page 24, exactly as printed in the chapter: five airflow rows (3,348 to 4,836 CFM, with outlet velocity 3,600 to 5,200 FPM) and eight static pressure columns (4 to 32 in. wg), each cell an RPM and a BHP at standard air. The header and footer are shown as on the page: impeller diameter 22.625 in., tip speed 5.92 × RPM, outlet area 0.93 ft², FEG80; maximum RPM Class 22 = 2,812, Class 32 = 3,337, Class 45 = 4,000; installation type B and D; BHP without transmission losses; no appurtenance effects. The two underlined cells (4,836 CFM at 28 and 32 in.) mark maximum static efficiency.

For each of six duty points the learner types an RPM and a BHP and picks Class 22, 32 or 45, then presses Check:

# Duty Method RPM BHP Class
1 4,092 CFM at 12 in. Direct 2,167 11.72 22
2 3,720 CFM at 24 in. Direct 2,879 21.02 32
3 4,836 CFM at 32 in. Direct 3,340 35.65 45
4 4,000 CFM at 12 in. Interpolate CFM 2,157 11.42 22
5 4,000 CFM at 14 in. Interpolate CFM then SP 2,291 13.18 22
6 4,464 CFM at 30 in. Interpolate SP 3,224 31.08 32

Rules: linear interpolation \( y = y_1 + \frac{x - x_1}{x_2 - x_1}(y_2 - y_1) \); for a point between two pressure columns, interpolate airflow in each bracketing column first, then pressure between the two results. Direct readings must match exactly (±1 RPM, ±0.01 BHP); interpolated answers must be within ±1% of the RPM and BHP above. Class is 22 when RPM ≤ 2,812, 32 when 2,812 < RPM ≤ 3,337, and 45 when 3,337 < RPM ≤ 4,000. A duty point is correct only when all three answers are.

Each point has two attempts; the first is scored. Check marks each of RPM, BHP and class with ✓ or ✗. Once the point is resolved (correct, or the second attempt) the class overlay turns on (shaded bold = Class 32, shaded italic = Class 45), so both answers must come from the footer speeds. A correct answer gives the row, column and class reasoning; a first wrong attempt names which answers are wrong and gives a hint (the slip or the method step, never a value or the class); after the second attempt the answer and its calculation are shown. The overlay turns off when the next point loads. The score reads "Duty points correct: n of 6" (first attempts); mastery is 5 of 6. After point 6 the summary lists the points not right on the first attempt with their answers.

The scratch panel is a notepad: click cells to pin up to four bracketing values (or move with the arrow keys and press S) and type the fraction f you worked out. It echoes what you entered and never computes the answer. Hovering a cell highlights its row and column heads. All values must be confirmed in Fan Selector before quoting.

How to Use

  1. Read the duty point. Is it on a printed row and column, between two rows, between two columns, or both?
  2. Find the bracketing cells; pin them in the scratch panel if that helps.
  3. Type the RPM and BHP, choose the class by comparing your RPM with the footer, and press Check. If you have an attempt left, correct the marked answers and check again.
  4. Press Next duty point. After point 6 read the summary, explore the grid with the overlay, and press Start over to repeat.

Keyboard: Tab moves through the RPM box, the BHP box, the class buttons and the other buttons; Enter checks (from either box), then goes to the next point and starts over from the summary. Outside a text box, the arrow keys move a cell cursor over the grid (each cell is read aloud) and S pins or unpins that cell.

Data label: "Source: TCF Catalog 902 (Nov 2017) p. 24 · Confirm in Fan Selector before quoting", shown at the bottom left of the drawing.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://moroshek.github.io/FanTASTIC-textbook/sims/ch26-performance-table-reader/main.html"
        height="709px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Learning Objective

The learner will use an excerpt of the RBA 913 performance table to find the RPM and BHP for a duty point, by direct reading or linear interpolation within ±1%, and to name the fan class the point requires (Bloom: Apply, verb: use).

Audience

Adult professional development: new application engineers, sales staff, representatives and facilities staff.

Duration

15 minutes

Prerequisites

Performance table, performance table header, outlet velocity, class shading and interpolation, all defined in the section "Performance Tables" of Chapter 26.

Activities

  1. Read (4 min): Points 1 to 3 are direct readings. Before checking point 3, compare its RPM with the Class 32 limit digit by digit.
  2. Interpolate (8 min): Points 4 to 6. Write f and each intermediate RPM and BHP in the scratch panel before typing the answer. For point 5, interpolate airflow in both the 12 in. and 16 in. columns before interpolating pressure.
  3. Explore (3 min): After the summary, turn the overlay on and trace where Class 32 begins in each row. Why does the boundary not follow a straight column?

Common Misconceptions Addressed

  • The class is decided by the static pressure column alone: points 2, 3 and 6 put Class 32 and Class 45 in columns that also hold other classes; the 32 in. column holds both.
  • Interpolation can use the nearest cell instead of the two bracketing cells: the ±1% tolerance on points 4 to 6 rejects a nearest-cell reading.
  • A duty point between two pressure columns can be interpolated in one step: point 5's feedback spells out the two steps.

Assessment

  • Score "Duty points correct: n of 6" counts first attempts; mastery is 5 of 6. Second attempts, hovering and the overlay are not evidence of mastery.
  • Follow-up question: a duty of 4,836 CFM at 30 in. comes out near 3,246 RPM. Which class do you order, and what would you check before quoting it?

References

  1. Chapter 26: Reading Catalogs and Performance Tables - performance table header, reading a table, class shading and interpolation worked examples.
  2. Twin City Fan Catalog 902, RB Industrial Fans (PDF) - page 24, RBA 913 performance table, maximum RPM by class and rating notes.
  3. Twin City Fan Product Catalogs - current editions and the Fan Selector software that computes points directly.
  4. p5.js - the JavaScript library used to draw the table.