Lecture 9: Evaporation

2y ago
13 Views
2 Downloads
5.70 MB
52 Pages
Last View : 27d ago
Last Download : 1m ago
Upload by : Jenson Heredia
Transcription

Lecture 9: EvaporationKey Questions1. What is a evaporation?2. Why does evaporation cool water?3. What are the main energy inputs into a lake?4. What is a vapor pressure deficit?5. How does wind sustain lake evaporation?6. What cause lake effect snow?evaporation

Evaporation is the net loss of water from a liquid surfacethat results from a phase change from a liquid to a vapor.It is a net process because water vapor is constantlymoving back and forth from the water surface.Evaporation occurs when there are more moleculesleaving the water surface then entering.water surface

Remember, water is a polar molecule. Liquid water is acollection of molecules connected by hydrogen bonds.water is polar

It takes energy for a molecule to break a hydrogen bondand escape the water surface.water surface

Phase changes involve heat (energy) exchanges (latent heat )condensation releases heatvaporliquidevaporation requires heat

The collective motion of water molecules in the water iscalled kinetic energy. The average kinetic energy of themolecules quantifies the water temperature.

Molecules with the highest kinetic energy can break thehydrogen bonds and escape the water surface.Thus, reducing the water temperature because theaverage kinetic energy is reduced (heat is removed).water surface

Evaporation cools off the water!

Evaporation cools off the water!

Swamp Cooler (evaporation cools)http://www.pinnacleint.com/evap.html

water vaporcooling towers are designed toevaporate, hence cool water

What drives evaporation?1) Energy input to the water to supply heat (i.e., increasethe kinetic energy so molecules can escape).2) Diffusion of water vapor molecules from the water surface to theatmosphere.3) Transport of water vapor molecules away from the water surface.

Heat Inputs1. Solar radiation is the main source of heat to a lake.water surface

Heat Inputs1. Solar radiation is the main source of heat to a lake.The amount of solar radiation depends on the time of year and latitude.

Heat Inputs1. Solar radiation is the main source of heat to a lake.The amount of solar radiation depends on the time of year and latitude.

North Shore Meteorological (MET) StationMeasures rain, temperature, humidity, wind speed,wind direction, and solar radiation

Solar Radiation (W/m2)Average daily solar radiation collected atthe North Shore MET stationJanJulDec

Ag weather stations collect solar radiation data

Heat Inputs2. Longwave radiation (heat) reflected off the cloudswarmwater surface

Heat Inputs3. Sensible heat - heat conducted to the water from the warm airwarm airwater surface

Modeled Heat Inputs into Lake WhatcomSolarOctSensibleAprLongwaveSep

What drives evaporation?1) Energy input to the water to supply heat (i.e., increasethe kinetic energy so molecules can escape).2) Diffusion of water vapor molecules from the water surface to theatmosphere.3) Transport of water vapor molecules away from the water surface.

Actual vapor pressure is a measure of the amount of watervapor molecules present in a given parcel of air.ea actual vapor pressurelow vapor pressurehigh vapor pressure

Saturation vapor pressure is the maximum amount of water vapor aparcel of air could hold at a specific temperature (which decreaseswith temperature).esat saturation vapor pressurecool air has a lowsaturation vapor pressurewarm air has a highersaturation vapor pressure(more water molecules)

Saturation vapor pressure is the maximum amount of water vapor aparcel of air could hold at a specific temperature (which decreaseswith temperature).

If warm, humid air is cooled offwater vapor will condensebecause the saturationvapor pressure decreases

Relative humidity is the ratio of the amount of water vapor in a parcelof air (absolute vapor pressure) to how much water vapor the parcelcould hold at a given temperature (saturation vapor pressure).actual vapor pressurerelative humidity X100saturation vapor pressureDew point temperature is the temperature at which a parcel of airreaches saturation.

Diffusion or Vapor Transferthin boundary layer of air that is fixed at the water temperaturewater surfacewater temperature

Diffusion or Vapor Transferthe boundary layer is always saturated with water vaporwater surfacewater temperature

Diffusion or Vapor Transferthe magnitude of the vapor pressure is determined by the water temperaturewater surfacewater temperature

Diffusion or Vapor Transferhigher vapor pressurewater surfacewarm water

Diffusion or Vapor Transferlow vapor pressurewater surfacecool water

VariablesTair temperature of the airTw temperature of the waterea actual vapor pressure of the airesat(Tair) saturation vapor pressure of the airesat(Tw) saturation vapor pressure of the boundary layeresat(Tw) - ea is called the vapor pressure deficit

Diffusion or Vapor TransferTaireaesat(Tw)water surfaceTw

Diffusion or Vapor Transfer (evaporation)If ea esat(Tw) then molecules will diffuse from the boundary layer to the airTaireaesat(Tw)water surfaceTw

Diffusion or Vapor Transfer (no net evaporation)If ea esat(Tw) then molecules will diffuse back and forthTaireaesat(Tw)water surfacecool water

Diffusion or Vapor Transfer (condensation)If ea esat(Tw) then molecules will diffuse from the air to the boundary layerTaireaesat(Tw)water surfacecool water

What drives evaporation?1) Energy input to the water to supply heat (i.e., increasethe kinetic energy so molecules can escape).2) Diffusion of water vapor molecules from the water surface to theatmosphere.3) Transport of water vapor molecules away from the water surface.

Diffusion or Vapor TransferWind sustains the deficit by sweeping moist air away from the water surfaceif ea esat(Tw) then evaporation continuesTaireahigh deficitlow deficitesat(Tw)water surfaceTw

I use a numerical model based on the Penmanmethod and data from the MET station to estimate theevaporation off of Lake Whatcom each year.Lake Whatcom

inchesModeled evaporation from Lake Whatcom in 2009-2010(about 20 inches total)OctAprSep

On a sunny summer day, the lake evaporates aboutas much water as the City of Bellingham withdrawalsin a given day - about 20 million gallons!Lake Whatcom

Lake Powel (Utah/Arizona) is a reservoir on the Colorado River.It evaporates about 10 feet of water per year.Glen Canyon Dam

Evaporation pans are used to estimate lake evaporation

Lake Effect Snow

Lake Effect Snow

Lake Effect Snow

Lake Effect Snownasaimages.org

Evaporation is the phase change from liquid to a vaporWhich beaker evaporates more water and why?covergroundwater rechargehot waterice bath

Lecture 9: Evaporation. Key Questions. 1. What is a evaporation? 2. Why does evaporation cool water? 3. What are the main energy inputs into a lake?

Related Documents:

Introduction of Chemical Reaction Engineering Introduction about Chemical Engineering 0:31:15 0:31:09. Lecture 14 Lecture 15 Lecture 16 Lecture 17 Lecture 18 Lecture 19 Lecture 20 Lecture 21 Lecture 22 Lecture 23 Lecture 24 Lecture 25 Lecture 26 Lecture 27 Lecture 28 Lecture

Georgia Tech ECE 6450 - Dr. Alan Doolittle PxTePe evaporation H NkT o Ea kT 31012 3 2 1 2 // J P kTm 2 2 R m k P T Area d r evaporation 24 22 For evaporation, the vapor pressure is, where is the surface tension of the liquid, N i

Lecture 1: A Beginner's Guide Lecture 2: Introduction to Programming Lecture 3: Introduction to C, structure of C programming Lecture 4: Elements of C Lecture 5: Variables, Statements, Expressions Lecture 6: Input-Output in C Lecture 7: Formatted Input-Output Lecture 8: Operators Lecture 9: Operators continued

The American Petroleum Institute Manual of Petroleum Measurement Standards (API MPMS) Chapter 19 details equations for estimating the average annual evaporation loss from storage tanks. These equations are based on test tank and field tank data and have been revised since initial publication for more accurate estimations. WHAT IS EVAPORATION? Evaporation is when a substance changes from the .

Lesson plan on investigative science Evaporation Based on results from TIMSS 2015. 2 Evaporation Pupils performed less well in the TIMSS test when assessed on applying their knowledge of evaporation in real life contexts. Lessons 1 and 2 provide teachers with classroom activities for

Lecture 1: Introduction and Orientation. Lecture 2: Overview of Electronic Materials . Lecture 3: Free electron Fermi gas . Lecture 4: Energy bands . Lecture 5: Carrier Concentration in Semiconductors . Lecture 6: Shallow dopants and Deep -level traps . Lecture 7: Silicon Materials . Lecture 8: Oxidation. Lecture

TOEFL Listening Lecture 35 184 TOEFL Listening Lecture 36 189 TOEFL Listening Lecture 37 194 TOEFL Listening Lecture 38 199 TOEFL Listening Lecture 39 204 TOEFL Listening Lecture 40 209 TOEFL Listening Lecture 41 214 TOEFL Listening Lecture 42 219 TOEFL Listening Lecture 43 225 COPYRIGHT 2016

The Zipwhip Messaging API supports both single -user and multi-user authentication. If you use single-user authentication, then all users are Administrators (Admin). There is a single tier of users. If you use multi-user authentication, then at least one user is the Administrator and all other users are Operators. There are two tiers of users .