Ventilation Definition and 34 Threads

Passive ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural forces. There are two types of natural ventilation occurring in buildings: wind driven ventilation and buoyancy-driven ventilation. Wind driven ventilation arises from the different pressures created by wind around a building or structure, and openings being formed on the perimeter which then permit flow through the building. Buoyancy-driven ventilation occurs as a result of the directional buoyancy force that results from temperature differences between the interior and exterior. Since the internal heat gains which create temperature differences between the interior and exterior are created by natural processes, including the heat from people, and wind effects are variable, naturally ventilated buildings are sometimes called "breathing buildings".

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  1. druidhr

    HVAC Fan for tube 5" in diameter and 160ft long

    Hello, I have question about vent for tube that is 5" in diameter and 160ft long. Could 5" vent push/extract air to/from tube above? If possible, how much CFM should vent have? Thx 😊
  2. J

    Underground pump vault airflow considerations

    Hello, I am currently designing and building a small utility vault to house a centrifugal pump for a water fountain, and I am specifically concerned with providing adequate ventilation not only during operation but also in general to reduce moisture and corrosion of the equipment. While all of...
  3. A

    B How long does it take to reach harmful CO2 levels in a room?

    • I exhale 1 kg of CO2 per 24 hours = 41.67g/h (average) • Co2 indoors after ventilation = outdoors = 400 ppm (world average) • Co2 indoors threshold = 1000 ppm (cognitive effect) • Room volume = 32.5 m3 • Details to neglect: window and door closed tight, no HVAC system or other ventilation...
  4. T

    Mammalian Enteral Ventilation - a new way to breathe

    From: https://www.cell.com/med/fulltext/S2666-6340%2821%2900153-7?utm_source=EA Blood oxygenation through the lower intestinal tract is demonstrated in both mice and pigs. It is hoped this wiil work for those Humans that need temporary assistance with respiratory function. Inspired by...
  5. russ_watters

    Lab Ventilation Energy Use and COVID

    Welcome to PF! I'm an HVAC engineer and I actually gave a talk/round-table with the founder of your organization a few years ago: https://www.westchesterbiotechproject.org/innovation-in-research-2017 One factoid I give on labs that speaks to what people know is that a single 8' constant volume...
  6. G

    Convection powered bladeless fan style ventilation?

    I'm still trying to understand the operation of these fans. How does the geometry downstream influence the flow. Specifically, there is an 8" ventilation tube in the ceiling of my warehouse. I'm thinking that I can extend it until it is 3/4 of the way to the floor. If I crack open an overhead...
  7. Jehannum

    Problem / conflict with gas appliance ventilation standard

    Unflued gas appliances emit all of their combustion products into the room in which they are installed. In the UK, ambient carbon dioxide in the commercial workplace is limited to 2800 ppm. The UK/European standard BS EN 13410 (and many appliance manufacturers) give the formula for mechanical...
  8. anorlunda

    Is Ventilation Necessary for Safe 3D Printing?

    :warning: Sigh. Yet another hazard to worry about. You can just order a 3D printer online, plug it in, and start using it. But you shouldn't do that until you provide adequate ventilation.https://www.zdnet.com/article/volatile-compounds-3d-printing-has-a-serious-safety-problem/
  9. D

    CO2 [ppm] exposure relative to room volume [m^3] and air ventilation

    Hi All, I am trying to find out how much CO2 (ppm) would be released into a ventilated room (m3) from a faulty pressurized gas cylinder to calculate risk associated. Would anyone be able to help me with a formula? I was trying to work with V=nRT/P but wasn't sure how do I translate the outcome...
  10. M

    Which fan/pipe combination is the most efficient?

    I'm making a ventilation system with a fan that will blow air through a 1700mm long pipe that has a 45 degree bent in the middle. I should decide on a pipe diameter of 125mm or 160mm. Also I need to choose between 3 different fans that has the following specs from the manufacturer: 120mm fan...
  11. longz

    Pressure loss to double wall pipe (ventilation)

    Hi every body, I need help to calculate the pressure drop to double wall pipe with information as below, i understand need calculate pressure loss to the straight pipe, elbows and supports but I don't know exactly how. - Fluid : air - Double wall pipe (stainless steel) with outer pipe...
  12. T

    Modeling Jet Fans in Parking Ventilation in Ansys CFX

    Hi , I'm new to CFD. I'm modeling a parking ventilation system in ansys CFX. I'm having some trouble modeling the jet fans . I went as follows. I created a fresh air inlet (Opening BC), an exhuast outlet (outlet BC) and in the middle I distributed jet fans .The jet fans are modeled as sub...
  13. T

    CFD Modeling of a Jet Fan Parking Exhuast Ventilation System

    Hey Guys, I want to verify the exhuast design of a car park ventilation system on Ansys Fluent. Basically, I have jet fans distributed throughout the parking displacing air towards a certain point where I will extract it . How would you go about modeling the boundary conditions in this...
  14. W

    Lifting of submerged pipe, ventilation area calculation

    Hello all, This is the situation: a pipe, shown in de drawing below, is lifted at a constant speed of 1m/min. The pipe is closed at the top and open at the bottom. For obvious reasons, a ventilation hole is required at the top. The intention is to lift a minimum amount of water, in other words...
  15. A

    Natural ventilation through single opening

    Hello, I am wondering what will happen if I try to ventilate a room by natural ventilation through a single opening. In this opening there will be a ventilation grill. I already found a paper about counterflow through an open door by temperature differences...
  16. T

    Ventilation Requirements of different Labs

    Hey, Could someone please help me find a comprehensive source that might tell me anything about the functions of the following Labs (These Labs are found in an agricultural laboratory) Preparation room Mixer's Room Stability Analysis Lab Mineral Analysis Lab Chemical Storage Blood Analysis Lab...
  17. D

    Flow through Interconnected Tubes

    Hello all, this is my first post here, so please excuse me if there are any mistakes or important information is left omitted. Now, my problem is quite intricate and specific so I will be thankful for any information I can get. Using Excel, I am looking to model the volume flow of air through...
  18. S

    Room Pressure from Ventilation & Exhaust Rates

    If I am trying to estimate a room pressure (not having any measurement devices), could I estimate it as follows: Vo = Volumetric Air flow rate supplied into Room Ve = Volumetric Air flow rate exhausted from Room out to atmosphere Pf = Static Pressure Capability of fan Pr= Pressure of...
  19. A

    Design of forced ventilation system for gas reciprocating engine

    Here is the real life problem I am facing: Gas reciprocating engine is situated in an engine room. The engine is primarily cooled by jacket water flowing to remote radiator. The engine surface must also be cooled by forced convection to maintain max air inlet temp of 40C. Ambient can reach as...
  20. N

    What is the Recommended Ventilation Rate for a Brewery?

    Hi All, I'm designing an exhaust system in brewery. Does anyone know the recommended air changes (ventilation rate)? My concern is the elevated level of carbon dioxide during the fermentation process. I'm planing on exhausting the air thru sidewall propeller fans and make-up the air thru roof...
  21. U

    What Is the Ventilation Box Near the Floor?

    Hi all; an easy question for you. In the following picture, what is the ventilation box in the corner near the floor? Is there a particular name for these things? I see them everywhere. http://upload.wikimedia.org/wikipedia/commons/7/76/Duracraft_pedestal_fan.jpg Thanks!
  22. X

    Airflow for engine room ventilation

    hello fellow engineers! i just started work at a marine company and was assigned to investigate on this formula. it is from ISO 8861 and used to caculate the airflow needed for heat evacuation in a engine room. this is the formula, airflow needed = (heat emitted from engine and all other...
  23. H

    Placing air suction next to the air flow ventilation of a PC. Good or bad idea?

    This is something that came up at work, as there are four computers running with their air vents placed four to six inches away from the air suction (so that it would suck up the air which was blown out from the air vent fan of a PC.) While this may seem like a good idea on paper (as the suction...
  24. C

    Ventilation Fitting Pressure Loss Coefficients

    Good morning, I'm calculating the pressure loss of a ventilation system for pot-off gas of an aluminum smelter using ASHRAE tables for fitting loss coefficients. The problem is that for much of the ducting, the diameters and flowrate ratios I have do not exist in the tables. (We're talking...
  25. S

    How Long to Ventilate Linked Rooms to Safe Nitrogen Levels?

    Homework Statement There are two storage rooms, (A) and (B) connected by a single doorway. Only room (B) has an outward vent, so all air exiting the rooms does so through this vent in room (B). The ventilator you will install drives outside air (78% nitrogen) at a certain flow rate through a...
  26. N

    Where does this steel ventilation calculation equation come from?

    I'm looking at a vent that will be used to prevent a tank from collapsing due to vacuum pressures in a pipe burst/free drain scenario. The situation would be a container is filled with water when an inlet or an outlet pipe bursts. The water flowing out would create some pressure in the tank...
  27. A

    Is Displacement Ventilation a Viable Option for Cooling in the Northeast USA?

    Any of you HVAC guys/gals design a Displacement Ventilation (DV) system in the Northeast USA? With our heating requirements as a notable concern, is DV a viable option for very many applications in the NE USA (DE, NJ, PA areas). It looks interesting to me especially for cooling, but I...
  28. J

    Why Do We Breathe More Fiercely During Vigorous Exercise?

    Ventilation (concept problem), please help We breathe more fiercely when we do vigorous exercise. But what is the reason behind? (1) The medulla oblongata senses the increase in blood CO2 concentration. (2) The receptors in our skeletal muscles send nerve impulses to the brain. My...
  29. I

    How Are Power Panels Ventilated?

    How is ventilation maintained in Power Panels. Are there air ducts, at the sides etc. I haven't seen any exhaust fan mechanism as such on any Power Panels.
  30. D

    Air flow - roof and attic ventilation

    Hi all, I need to know if I'm on the right track with my thinking. I've drawn a diagram that hopefully is not too simplistic and shows what I am getting at. One of these links should work. http://www.roofersreview.com/d/9390-2/Hip+roof+diagram+calc_+copy.jpg...
  31. M

    Ventilation Systems: Calculating G & E Rates

    Hi...Prbably a stupid question but here it goes: I have some equations here, some of them have a G for rate of generation and others have E for rate of evaporation (both of them have units of volume per time). My question is: if I know that I have 3 galons of a chemical at the beggining of...
  32. T

    Calculating Ventilation Effect Watts in a Room

    I want to calculate how much effect in Watts a ventilation system brings into a room. Will it be correct to use the following equation for this: \dot Q = \dot V \cdot 0,335 \cdot \left( {T_A - T_O } \right) where 0,335 is actually the Cp of air derived from {{1005} \over {3600}} \cdot...
  33. K

    Engine room ventilation system

    How to calculate the air needed to cool the engine room and maintanin the temperature not to exceed 120F( for marine duty)with 2 engines of 1401bhp and 2-generator sets. What factors should i consider? i thought of taking the engineer room volume, heat dissipation from the engine and air intake...
  34. F

    Question About Ventilation In A Fish

    The flow of water and ventilation system in fish is 1 way, where as in mamals the flow of gases is in 2 ways. why is this?
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