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  • Users: MrReds
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  1. MrReds

    Water in a refrigeration cycle

    Hi Everybody, hope somebody can help me. I tried to search in old post but without success. I am trying to calculate some heat exchangers where water is utilized as refrigerant, that is: enters in the condenser as steam and condenses and it is evaporated in the evaporator (enters as water...
  2. MrReds

    pressure drop formula steam

    Hello Everybody, Please, I’d need some help from somebody Question may seem odd, but I have not found any literature reference neither past post has been useful. I have to calculate the pressure drop of a flux of water steam that condenses and becomes liquid water and a flux of water that...
  3. MrReds

    micro - mini - channels

    Hello Everybody ! Please, I'd need somebody put me things straight concerning definition of microchannels minichannels microtubes exc is there a reference dimension under which a tube can be defined a micro tube and over which is a tube ? which is the difference between micro channels and mini...
  4. MrReds

    friction factor and materials

    Hi all ! I am sorry to disturb you with a so banal question, but I'd need your help to clarify a basic doubt. This doubt is: if I use f = 0.046/Re^(-0.2) to calculate the friction factor, this factor is independent by tube material. This means that if I use this formula, if I have the same...
  5. MrReds

    radiators for domestic heating - thermosyphons

    Hi everybody ! I am contacting you concerning this issue: Is there, according to your knowledge, ad advised water velocity in a radiator used for domestic heating - the thermosyphons -? Should it be high, so that we get an higher internal heat transfer coefficient, or low, so that it would...
  6. MrReds

    Pulse Bruel

    hallo everybody my company is evaluating to buy a Pulse system from B&K to realize sound measurement. Please, does anybody utilizes it ? Could anybody suggest me any alternative ? Could anybody suggest me any link to see valid comments about this system ? Thanks in advance !
  7. MrReds

    Compressed air

    Hallo to everybody. I am facing to following problem: I have to calculate an heat exchanger to reduce temperature of compressed air. Please, I’d like to know if, according to your knowledge, there is something that differs from traditional heat exchanger dimensioning. Are there further...
  8. MrReds

    Log mean TD

    Hallo to everybody Please, I would be grateful if someone of you could help me in following issue: I am dealing with this issue, that it can be apparently simple, but I cannot find any reference about it. In an heat exchanger, when defining logarithmic mean temperature, Th1 = inlet...
  9. MrReds

    Dry Coolers and condensers capacity

    Hallo to everybody ! I have realized a research but I have not found anything useful about following issue in the previous posts. Therefore, I would be grateful if somebody could help me: For the condensers you can generally give the capacity in a standard condition and then you can analyze...
  10. MrReds

    Electrode Potential and kinetics

    Hallo to everybody ! Please, I’d like to know if somebody can help me in this issue: When I consider the galvanic couple of 1) aluminum and copper, the electrode potential of aluminum is -1.66V, while copper is +0.34V. As a consequence aluminum is the less noble metal and will be subjected to...
  11. MrReds

    Control & acquisition system

    Hallo to everybody ! Please, I am dealing with following situation: I have to choose between a system where acquisition system is realized by one brand, while control system is realized by a second one. The second possibility is to choose a single system, where acquisition & control are...
  12. MrReds

    Nusselt number calculation

    Hallo to everybody, Please, I’d need some clarifications concerning calculation of Nusselt numbers in tubes. Could you explain me when utilize Dittus-Bolter and when Gnielinski ? Are this correlations valid for both laminar and turbulent flow ? Should the fluid be steam, which correlation...
  13. MrReds

    R410A

    Hallo to everybody ! I don't know if I am posting in the right forum, but I'd try ! Please, I would be grateful if anybody could : - describe me his experience with R410A, with respect of R22 or R407C, for example, in terms of dimensioning heat exchangers, or dimensioning lines and - suggest...
  14. MrReds

    Gravity Coil

    Hallo to everybody ! Please, I have utilized the search function but I had no success. Could anybody explain me how is realized the calculation of the capacity of a gravity coil ? In my opinion, it should be a function of fin pattern and tube diameter - as for other coils, indeed -...
  15. MrReds

    Aluminum - alloys and corrosion - questions

    Hallo to everybody When using search function I have seen lots of threads concerning aluminum corrosion. Nevertheless, what I'd like to know is: could you kindly tell me is there a web page where I can find different properties of aluminum alloys ? Concerning corrosion of aluminum, do you...
  16. MrReds

    refrigerant charge

    hallo to everybody and thanks to who has answered to my previous posts! Please,I'm looking for some clarifications concerning this issue: - what happens to the cycle when I add some refrigerant charge ? What happens to condensing and evaporating pressures ? and to condenser subcooling and...
  17. MrReds

    Internal and external rotor

    Hallo to everybody ! Please, can anybody explain me the difference between internal and external rotor ? Thanks in advance
  18. MrReds

    Surface temperature of cooling coil

    Hallo to everybody ! I am posting also to this forum following question: I am trying to calculate a cooling coil (it's fin and tube heat exchanger). I know inlet conditions, water inlet and outlet conditions (or, alernatively, water mass flow), but I am looking for a formula to get the fin...
  19. MrReds

    Temperature of surface of cooling coil

    Hallo to everybody ! I am trying to calculate a cooling coil (it's fin and tube heat exchanger). I know inlet conditions, water inlet and outlet conditions (or, alernatively, water mass flow), but I am looking for a formula to get the fin temperature. This temperature is what I need to get the...
  20. MrReds

    optimal refrigerant pressure drop for condensers and coolers

    Hallo to everybody. Please, can anybody tell me if there are optimal pressure drops in a condenser and an evaporator as a function of different refrigerants ? Is there a preferable circuit disposition depending on refrigerant type (ex: R407-C, R410A)... thanks in advance for your help

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