Why a measured P-Q curve matters in a 35 mm blower
A compact centrifugal blower can look simple on a catalogue page. The engineering decision depends on what it delivers after the enclosure, heat source and outlet create resistance.
A 35 × 35 × 10 mm blower is used when the package is too tight for a larger fan and a straight-through axial path is not enough. The useful question is not “what is the maximum CFM?” It is “what airflow remains at the static pressure created by the real device?”
The DC3510 test record gives a worked example. At a measured 5 V input and 10,345 RPM, the sample reached 2.36 CFM at zero static pressure and 14.01 mmH₂O at zero airflow. Between those endpoints, eight measured points show how airflow falls as pressure rises. That curve is starting evidence, not a universal promise for every variant.
The report uses wind-tunnel and AMCA-210 method language. The sample model field is incomplete, so this article does not invent a part number. The result should be repeated on the customer enclosure before approval.
Read the test record before reading the curve
A P-Q curve is useful only when voltage, speed, air condition and units are visible beside it.
The record reports approximately 5.00 V, 10,345 RPM, 0.2386 A and 1.192 W for the sample test condition. The stated room condition is 29.7 °C with 75.9% relative humidity, while the standardised table uses a reference atmosphere. Changing voltage, speed, air density or test method changes the curve.
The workbook contains several unit views. The same curve is shown in CFM and mmH₂O, CMH and Pa, and L/s and inH₂O. Keep one primary unit pair in the article and label conversions clearly. Mixing CFM with Pa without conversion is a common review error.
Current, power and RPM vary slightly across the pressure points. For a production decision, record connector voltage and actual speed rather than assuming that a nominal 5 V label means one fixed operating condition.
| Item | Recorded value | Interpretation |
|---|---|---|
| Input voltage | 4.999868 V | Measured sample input |
| Speed at first point | 10,345 RPM | Actual test speed |
| Current / power | 0.238599 A / 1.192178 W | Electrical reference |
| Ambient condition | 29.7 °C / 75.9% RH | Recorded environment |
| Method note | Wind-tunnel / AMCA-210 language | Confirm acceptance method separately |
The eight points show the usable operating window
The endpoints are easy to quote. The intermediate points help an engineer decide whether the blower can overcome a real restriction.
The measured points run from 2.36 CFM at 0 mmH₂O to 0 CFM at 13.32 mmH₂O measured static pressure, with a standardised maximum of 14.01 mmH₂O at zero flow. Between them, airflow is 2.04 CFM at 2.23 mmH₂O, 1.69 CFM at 4.80 mmH₂O, 1.36 CFM at 7.43 mmH₂O, 1.02 CFM at 9.48 mmH₂O, 0.67 CFM at 11.04 mmH₂O and 0.33 CFM at 12.29 mmH₂O.
A designer who needs roughly 1 CFM should not select from the 2.36 CFM headline alone. The relevant region is close to 9.5 mmH₂O in this sample record, before the customer enclosure curve and temperature basis are added.
The curve is not a straight line. Use the measured point nearest the expected duty, then validate the installed point with the actual inlet, outlet, heat source, cable path and mounting condition.
Convert the device into a system resistance curve
The blower curve belongs to the fan. The enclosure, filter, grille, heat sink and outlet create the second curve.
Start with the heat source and define the airflow target from the allowed temperature rise. List every resistance between inlet and outlet: grille, narrow channel, heat sink, filter, cable bundle, bend, outlet mesh and seal. Each item consumes pressure at a particular flow.
The operating point is where the blower P-Q curve and system resistance curve intersect. If the intersection is below the required airflow, the zero-pressure headline will not solve the problem. A shorter restriction or larger outlet may be better than a faster motor.
Use the eight measured points as a lookup table. Do not extrapolate beyond the tested range and do not treat zero-flow pressure as a recommended operating point.
Why a centrifugal blower suits a tight 35 mm package
The right airflow architecture depends on path geometry, not on the word “blower” alone.
A compact centrifugal blower can turn the flow and push through a short restrictive path. That is useful for routers, set-top boxes, compact server accessories, optical electronics bays, LED drivers and other enclosures where inlet and outlet cannot be placed on opposite faces.
The trade-off is packaging. Outlet direction, inlet clearance, scroll geometry, mounting screws and cable exit affect the installed curve. A catalogue outline that fits mechanically can still fail if the outlet discharges into a wall or the inlet is blocked by a cover.
The DC3510 PDF shows a 35 × 35 × 10 mm A Type blower, plastic frame and impeller, 8.5 g fan weight, and catalogue examples across 5 V and 12 V. Treat those as variant references; the tested sample curve remains the evidence here.
Use electrical data with the airflow data
The test sheet records voltage, current, power and speed together because cooling performance has an electrical cost.
At the first measured point, the sample records about 0.239 A and 1.192 W at 5 V. As the pressure point changes, the workbook shows small changes in current, power and RPM. This matters in battery-powered or thermally constrained electronics where the fan itself contributes heat and energy consumption.
Validate startup at the lowest allowed voltage, stable operation across the command range, and feedback if the application depends on fan health. Confirm PWM, FG/RD, connector, cable length and ground reference with the actual variant.
If the customer needs another voltage, bearing option, speed band, noise target or connector, request a separate sample and curve. Do not copy the 5 V test into a 12 V design without evidence.
Validate noise, temperature and mounting after the P-Q match
A curve match is necessary but does not finish the engineering review.
The PDF lists catalogue noise values from 25.4 dB-A to 40.0 dB-A across the visible 5 V speed variants. These are catalogue references, not an installed acoustic guarantee. Panels, outlet turbulence, mount stiffness and tonal content can change what the user hears.
Test the sample at the actual enclosure temperature, with the real mounting torque, gasket, grille and cable path. Measure heat-source temperature and record connector voltage, RPM, current, pressure and airflow in the same record.
If the application is sensitive to vibration, inspect the frame and mount after the thermal sequence. A lightweight 8.5 g package can still transmit structural response if the mount couples it to a panel.
A practical DC3510 validation plan
Use the measured curve as the first gate, then close the gaps with an installed sample.
Define required airflow at the heat source and allowed pressure drop. Select a candidate point with margin rather than using the zero-pressure headline. Build the real enclosure path and repeat at customer voltage and temperature.
Record startup, steady state, feedback, current, power, temperature, pressure and airflow. Repeat after service access, cable routing and any filter or grille change. If the operating point moves, update the system curve instead of blaming the fan by label.
The acceptance record should name the exact sample, test voltage, speed, environment, instrument method and mechanical condition. The source workbook’s sample-model field is incomplete, so a production release should close that identification gap.
How MEGA Tech supports a custom blower program
MEGA Tech develops and manufactures custom cooling fans and supports the path from operating-point review to sample validation and volume production.
For a first review, send heat load, required airflow and static pressure at that airflow, inlet temperature, voltage tolerance, control interface, connector, envelope, outlet direction, noise target, vibration condition, environment, quantity and life assumption. We select by operating condition, not frame size alone.
MEGA Tech supports fan selection, air-path review, sample validation and volume production. The customer should validate the fan on the final enclosure because system resistance, heat source and acoustic boundary belong to the complete device.
We do not supply complete cabinets, heat exchangers, coils, liquid loops or system safety design. Start with the fan selection tool, review the DC axial fan range, inspect the 35 mm product family, or request a sample on WhatsApp.
Engineer FAQ: 35 mm blower P-Q testing
A custom fan sample is useful when the device constraint is clearer than the available catalogue choice.
MEGA Tech develops customized DC cooling fans and compact centrifugal blowers around the installed duty rather than selecting only by frame size. For a compact electronics, that can mean a different frame or thickness, connector and cable length, PWM response, FG or RD feedback, airflow direction, bearing configuration, mounting detail, or a blower outlet shaped around the enclosure duct. The correct choice depends on the pressure-flow requirement and the mechanical integration.
For a useful first review, share the fan envelope, voltage range, target airflow or pressure, inlet temperature, chamber temperature, control interface, connector pinout, noise limit, duty cycle, expected service life, filter or grille condition and the sample quantity. A drawing, photograph and short video of the failure can be more valuable than a catalogue part number when the problem appears only during motion or after a long test.
Our boundary is important: MEGA Tech supplies and customizes cooling fans and fan samples. We do not replace the device controller, heater, heat source, enclosure safety design, filtration certification or material process qualification. The final fan must still be validated by the device team in the real machine with its approved thermal and test-quality limits.
For startups, the same method works before the design is frozen. A small first build can answer whether the fan fits, starts at the required voltage, reaches the installed pressure, stays quiet during motion and protects the limiting component. Once the sample is accepted, the interface and test record become a clearer basis for pilot production and replacement planning.
Questions for a compact blower design review
These catalogue series may be suitable starting points for this application. Final selection depends on the installed airflow, static pressure, voltage, noise target and operating environment.
Request a sample for validation on your equipment.
From a curve to a validated sample
Short answers to the questions that usually appear during a compact electronics cooling review.
Q: Is maximum CFM the best way to choose a compact electronics fan? A: No. Use the installed pressure-flow point. A restrictive shroud, filter or grille can move the operating point far away from the free-air value.
Q: Should the heat source fan and part-cooling fan be the same? A: Not automatically. The heat source fan usually needs reliable continuous operation and heatbreak protection; the part fan needs controllable process cooling and a material-specific profile.
Q: Can a stronger part fan fix poor bridge quality? A: Sometimes, but first check outlet speed, layer time, duct distribution, material and the actual jet at the bridge. More airflow can also increase warping or reduce layer bonding.
Q: Does a closed chamber always improve testing? A: No. It can help some materials by stabilizing the process temperature, but it can also raise the inlet temperature of the heat source fan and overheat electronics. Separate the thermal zones and measure them.
Q: When is a centrifugal blower better than an axial fan? A: When the enclosure or enclosure has a compact, restrictive or turning air path that needs more pressure. Confirm the blower curve, outlet geometry, noise and mass in the actual assembly.
Q: What should a custom fan supplier receive before making a sample? A: The envelope, voltage, target airflow and pressure, temperature basis, PWM/FG/RD interface, connector, noise limit, mounting, environmental exposure, duty cycle and the test conditions that will approve the sample.
Questions for a compact electronics cooling design review
Use these questions to turn a fan discussion into a testable engineering requirement.
- Which fan duty is being specified: heat source cold side, part cooling, chamber circulation, electronics bay or filtered exhaust?
- What are the heat load, maximum inlet temperature, chamber target and allowed temperature rise at the limiting component?
- What is the complete pressure path, including the shroud, grille, filter, heat sink, bends and outlet?
- Where is the operating point on the fan P-Q curve, and what happens when the filter is loaded?
- What must PWM, FG or RD prove at startup, low duty, full duty and a fault condition?
- Does the moving enclosure pass clearance, vibration, noise and cable-flex checks over the full travel?
- Which materials, layer times, bridges and overhangs define the part-cooling acceptance test?
- What evidence will let the team approve the sample for production rather than only for a bench demonstration?
