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  • Users: EngAP
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  1. EngAP

    Effect of Uniform High Pressure on Structure of Polymers (HDPE & PU)

    I'd like to know how the properties of HDPE and PU vary when uniformly exposed to high pressure (up to 30MPa). Please discuss. Note that this is NOT a pressure vessel application.
  2. EngAP

    Plasticizers

    Is it correct that it is only really PVC that is able to absorb plasticizers in high (>20%) quantities? If not is it possible for Nylon to contain high quantities of plasticizers, specifically phthalates? I google searched with little success.
  3. EngAP

    Heat Sink Surface Finish & Flatness

    I am looking for information regarding heat sink surface finish and flatness. My particular problem is as follows: I have a small extruded aluminium heat sink (approx. 25mm long, 20mm wide and 13mm fin height) with 15W dissipated from a small (10 by 12mm) heater. The heater is screwed onto...
  4. EngAP

    Sarcasm

    After browsing these forums for a while I have noticed a lot of sarcasm in answers. Maybe some questioners desevre it for posting questions that a little hard work would solve but I have also seen it widespread in response to very good questions/answers. As an example I recently replied to a...
  5. EngAP

    Dimensioning Hole Wizard Holes in a Drawing

    Hi, I have never worked out how to automatically dimension holes created using the Hole Wizard in a drawing. If anyone knows could you help. Thanks.
  6. EngAP

    Estimating Heat Transfer Coefficient

    With refernce to my previous thread (Wind Adjusted Heat Transfer Coefficient) I need to estimate the heat transfer coefficient on the inside surface of a sealed enclosure. The air in the enclosure is 20degC hotter than the ambient (0degC with ambient at -20degC). There is a heater and fan...
  7. EngAP

    Wind Adjusted Heat Transfer Coefficient

    I would like a rough estimate of the heat transfer coefficient on the outside of an enclosure exposed to the wind. In (relatively) static air the coefficient has been approximated to 7W/m^2-K through experiment, with total surface area 0.2m^2. Would a value of 250W/m^2 be a useful starting...
  8. EngAP

    Y+

    I am having trouble understanding the use of Y+ when creating the boundary layer. I understand that it is important to ensure the boudary layer is detailed enough to capture the physics but also to use the minimum number of cells. Could someone help me in my understanding of the use of Y+ to...
  9. EngAP

    Natural Convection Heat Sink Analytical Model

    I need to learn how to create an analytical model of plate fin natural convection heat sinks to estimate the thermal resistance from component to air. I have had no luck searching for papers, texts or online guides. I have found several online calculators but I would like to create my own...
  10. EngAP

    Finite Element for High Cycle Fatigue

    I am looking for a finite element package to model high cycle fatigue failure. Are there any free packages available and if so, which are recommended? Thanks.
  11. EngAP

    Manufacture Design Guide and Process Texts

    I would like to know recommendations for texts detailing general manufacturing processes (forming, processing, machining etc. etc.) with focus on the practicalities of the processes and detailed design guidelines to allow ease of manufacture. I have 'Manufacturing Engineering and Technology' by...
  12. EngAP

    Part Labels in an Assembly

    I have an assembly that requires the parts to be labelled with their names. The label must be fixed to a surface of the part so that it moves and rotates with the part as the part is moved around the screen. The labels should also be shown on any dwgs created from the assembly. I have...
  13. EngAP

    Junction vs. Case Temperatures

    Quick question from a mechanical engineer to electrical engineers: How much hotter is the junction temperature compared to the case temperature for a chip? Is there a range it is likely to fall within or is this a much too vague question? Specifically, if the spec for maximum junction...
  14. EngAP

    Minimising Solar Heat Gain

    I need to miminise solar heat gain through a small transparent plastic window of an electronics enclosure. I see two approaches: (1) Mimise the solar radiation transmitted into the enclosure and (2) maximise the thermal radiation transmitted out of the enclosure. Several questions: - The...
  15. EngAP

    Heat Loss from an Enclosure using Fourier's law & m.Cp.DeltaT

    Dear all, I have calculated the predicted heat loss from a sealed enclosure for various deltaT's (internal temperature to external temperature) using Fourier's Law and achieved reasonable accuracy, even when assuming to be through a straight wall rather than from an enclosure. The theory was...
  16. EngAP

    Solar Gain Calculation

    Hi all. I need to determine the temperature rise in a sealed enclosure due to solar radiation gain, with and without a sunshield. If anyone knows of a simple way of achieving this or any texts or links that may help then I would be grateful for any information. I would like to be able to...

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