# What is Moist air: Definition and 18 Discussions

Moist heat sterilization describes sterilization techniques that use hot water vapor as a sterilizing agent. Heating an article is one of the earliest forms of sterilization practiced. The various procedures used to perform moist heat sterilization process cause destruction of micro-organisms by denaturation of macromolecules.

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1. ### B Moist air - does it rise or drop?

A very simple question that i found some contradicting answers about. It's well known that cold air generaly will drop and hot air will rise. That is why if we open a window during winter time, it will feel almost like a wind is blowing through the window. That is great property that can be used...
2. ### Ipho 1987, thermodynamics problem: Moist air ascending over a mountain range

I'm struggling with explanation of part 3. I don't know why they are using adiabatic equation while the gas is constantly heated by condensating vapour. While we are deriving adiabatic equation we use the fact, that there is no additional heat put into the system. Thank you in advance.
3. ### Solving Entropy in Moist Air: No Violation of Law

Homework Statement When the air outside is very cold and dry, your climate control system must humidify the cabaret air so that the singers don't lose their voices. The climate control let's pure water evaporate into the dry air and raises the moisture content of that air. As this evaporation...
4. ### Entropy in Dry vs Moist Air

Homework Statement During the fall, the outside air's temperature is comfortable but its humidity is too high for direct use inside the cabaret. The air feels clammy and damp. So your climate control system chills the outdoor air to extract some of its moisture and then reheats that air back up...
5. ### What is the chemical formula for moist air at 20°C?

I am trying to find the chemical formula for moist air. By using an online psychrometric calculator, I find that moist air at 20°C has a mol fraction of water=0.0235 and mol fraction dry air=0.9765. Does this mean like this? 0.9765(O2 + 3.76N2) + 0.0235H2O ----> 41.55(O2 + 3.76N2) + H20 My...
6. A

### Why is Total Air Pressure Constant in the Study of Properties of Moist Air?

Why we assume total air pressure (dry air +water vapour) to be constant during study of properties of moist air even when it is being heated or cooled how it is possible that pressure is constant , on what basis it is assumed? I think locally there must be variation in total pressure also due...
7. ### The change in temperature of moist air

Homework Statement 1 kg of moist air and 1 g condenses. What will the change in the temperature of the moist air be? Heat of Vaporization = 2.5*10^6 J/kg 2. The attempt at a solution The moist air will warm due to condensation. Heat of Vaporization=2.5*10^3 J/g Specific heat at...
8. ### Adiabatic Saturation Process of Moist Air

I am facing some overwhelming doubts while trying to study 'Psychrometrics'.Currently I am bamboozled trying to understand the process of adiabatic saturation of moist air. Some of the textbooks claim that a true adiabatic saturation process proceeds along the line of constant enthalpy of moist...
9. ### Solving Psychrometry Questions: Room Temp & Water Vapor

As we all know that in atmospheric pressure (1 Bar) saturation temperature of water is 100 deg C. And the air contains mixture of dry air and water vapour. My doubt is here that the water needs 100 deg Celsius to change from liquid to vapour state then how can a normal room temperature air...
10. ### Converting humidity ratio to specific humidity

Hello PF! I have a very simple question on psychrometry. I had an argument with one of my professors regarding these two quantities, humidity ratio and specfic humidity. Humidity ratio is defined as mass of water vapor per unit mass of dry air. It's the one you can read from a psychrometric...
11. ### Density of moist air at high temperatures?

I've spent hours trying to understand conceptually how to find the density of moist, hot air at high temperatures, eg at 600° C. Any help would be great. This is not a homework problem, but I'm preparing for a problem i will likely encounter shortly at work, and thermo is outside my specific...
12. ### Mass of Condensed Water Out of a Moist Air Stream

I am currently attempting to determine the amount (mass) of water that is condensing during a temperature change inside of a heat exchanger. Inititial Temp is 300°F, Initial Pressure is 19.696psia (5psig) in the air stream, Initial %RH is 5%. Final Temperature is 129°F and becomes 100% RH at...
13. ### Calculate RH of moist air at higher temp ranges accurately?

Calculate RH of moist air at higher temp ranges accurately? Hey there :) Im using the Magnus relation for calculating the RH of air (sat pressure the RH) only to find it works good only for temperature ranges upto 100°C (with corrections to original Magnus relation!) Does anybody know a...
14. ### General formula for refractive index of moist air?

Not sure if one exists but can anyone point me in the right direction? Looking for a formula which includes the temperature and partial/total pressure dependencies? I'm trying to find the trajectory of a photon through a cloud of varying (but known) temperature, pressure and humidity. If...
15. ### Calculating Moist Air Density

Hello All, I am trying to calculate the density of moist air. Am i correct in saying... density of dry air = 1.2754 kg/m^3 Now i can convert this to mmol/m^3 and density of dry air = 4.384692933394098e+04 mmol/m^3 at a given point in time density of CO2 in air = 16 mmol/m^3...
16. ### Thermodynamics-psychrometry question, mixing two streams of warm moist air

Homework Statement I'm trying to determine how to go about attacking this problem that I'm doing to I have 2 streams of air mixing, and I'm trying to find the temperature and relative humidity of the third stream. Stream 1: 2bar, 20C, 40%rh, and 1kg/s Stream 2: 1bar, 20C, 4kg/s So...
17. ### Is there any difference in a wave if its in dry air or moist air? Please help me out.

Homework Statement A) A tuning fork is struck in dry air. Then it is struck in moist air. Under whch conditions do the sound waves from the tuning fork move more quickly? B) No matter what the temperature if the air, the frequency produced by a tuning fork remains the same. Would the...
18. ### Understanding Enthalpy Change in Cooled, Moist Air

Genrerally it's so that hot air has larger enthalpy value than cold air. But is it also so that if you cool air and add water to it at the same time, the enthalpy will stay the same? How will the temp of the water affect the situation?