Critical Heat Flux Apparatus
Product Code : EL-HTL-11090
Quick answer: The critical heat flux apparatus demonstrates pool boiling on a thin electrically heated wire, from natural convection through nucleate and film boiling to burnout. A 10 cm test wire of 35 or 40 gauge sits in water in a glass trough, and a dimmerstat, voltmeter and ammeter set and measure its heat flux. Lab Exports manufactures it in Delhi for engineering colleges, polytechnics and TVET institutes.
Specifications
| Component | Specification |
|---|---|
| Test wire | 35 or 40 gauge, 10 cm long |
| Water heater | Nichrome, 1 kW |
| Trough | Glass, deep enough to submerge the test wire |
| Wire power control | Dimmerstat |
| Power measurement | Voltmeter and ammeter |
| Observation | Table light |
| Services | 220 V, 15 A stabilised single-phase supply; floor surface 1 x 1 m at working height |
How the critical heat flux experiment is done
When a surface under water is heated more and more strongly, boiling passes through distinct regimes. At first heat leaves by natural convection; then bubbles form at nucleation sites and nucleate boiling carries very high heat fluxes for a small temperature rise. At the critical heat flux the bubbles merge into a vapour blanket, heat transfer collapses and the surface temperature jumps, which for a thin wire means burnout.
The heat flux at the wire surface is q = V I / (pi d L), where d is the wire diameter and L the 10 cm length. Students compare the burnout value with Zuber's prediction for pool boiling, q_max = 0.149 hfg rho_v^0.5 (sigma g (rho_l - rho_v))^0.25, where sigma here is the surface tension.
- Fill the trough with water and bring it to the test temperature with the 1 kW heater.
- Connect the test wire and switch on the table light.
- Raise the wire voltage slowly with the dimmerstat, recording voltage and current at each step.
- Watch the change from convection to bubble formation and vigorous nucleate boiling.
- Note the voltage and current at the moment the wire burns out, then repeat with a new wire.
Key features
- Glass trough and table light for a clear view of every boiling regime
- Test wire heated directly by the current through it
- Choice of 35 or 40 gauge wire for comparative tests
- Dimmerstat for a gradual increase of heat flux
- Voltmeter and ammeter to measure the wire input
- 1 kW nichrome heater to hold the water temperature
Documentation and supply
Installation instructions and a manual are supplied with the apparatus. Most Lab Exports products carry a one-year manufacturer warranty.
Lab Exports manufactures the critical heat flux apparatus at its works in Laxmi Nagar, Delhi, and supplies it to engineering colleges, polytechnics and TVET institutes in India and 60+ countries, handling the export documents for each shipment. More about the company is on the About Lab Exports page.
Related Heat Transfer Lab products
- Stefan-Boltzmann Apparatus (EL-HTL-11089)
- Concentric Tube Heat Exchanger (EL-HTL-11091)
- Emissivity Measurement Apparatus (EL-HTL-11088)
- Shell Tube Heat Exchanger Water to Water (EL-HTL-11092)
- Heat Transfer in Agitated Vessel (EL-HTL-11087)
- Plate Type Heat Exchanger Apparatus (EL-HTL-11093)
The full range is in the Heat Transfer Lab section of the Engineering Lab range.
Frequently asked questions
What is the critical heat flux?
It is the highest heat flux reached in nucleate boiling. Beyond it a vapour film covers the surface, heat transfer drops sharply and a thin wire burns out.
Which test wires are used?
Test wires of 35 or 40 gauge, 10 cm long, heated by passing current directly through them.
What is the price of the critical heat flux apparatus?
Prices are not published on the website. Add the critical heat flux apparatus to the Enquiry Cart with the Add To Cart button on this page, or email [email protected] with the house code EL-HTL-11090 and the quantity, to receive a quotation.
Does Lab Exports manufacture the critical heat flux apparatus?
Yes. Lab Exports manufactures the critical heat flux apparatus at its works at 11/315, Lalita Park, Laxmi Nagar, Delhi 110092, under house code EL-HTL-11090.
Request a quote
Email [email protected] with the house code EL-HTL-11090 and the quantity, or add the critical heat flux apparatus to the Enquiry Cart with the Add To Cart button on this page. Tender buyers can also see the Tenders and OEM page.