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3-1 Adiabatic Compression
Solution Physics 213 Problem 1 Week 3 Adiabatic Compression a) Last week, we considered the problem of isothermal compression: 1.5 moles of an ideal diatomic gas at temperature 35oC were compressed isothermally from a volume of 0.015 m3 to a volume of 0.0015 m3. The pV-diagram for the isothermal process is shown below. Now we consider an adiabatic process, with the same starting conditions and the same final volume. Is the final temperature higher, lower, or the same as the in isothermal case? Sketch the adiabatic processes on the p-V diagram below and compute the final temperature. (Ignore vibrations of the molecules.) α α For an adiabatic process ViTi = VfTf , where α = 5/2 for the diatomic gas. In this case Ti = 273 o 1/α 2/5 K + 35 C = 308 K. We find Tf = Ti (Vi/Vf) = (308 K) (10) = 774 K. b) According to your diagram, is the final pressure greater, lesser, or the same as in the isothermal case? Explain why (i.e., what is the energy flow in each case?). Calculate the final pressure. We argued above that the final temperature is greater for the adiabatic process. Recall that p = nRT/ V for an ideal gas. We are given that the final volume is the same for the two processes. Since the final temperature is greater for the adiabatic process, the final pressure is also greater. We can do the problem numerically if we assume an idea gas with constant α. γ In an adiabatic processes, pV = constant, where γ = (α + 1) / α. -
Influence of the North Atlantic Oscillation on Winter Equivalent Temperature
INFLUENCE OF THE NORTH ATLANTIC OSCILLATION ON WINTER EQUIVALENT TEMPERATURE J. Florencio Pérez (1), Luis Gimeno (1), Pedro Ribera (1), David Gallego (2), Ricardo García (2) and Emiliano Hernández (2) (1) Universidade de Vigo (2) Universidad Complutense de Madrid Introduction Data Analysis Overview Increases in both troposphere temperature and We utilized temperature and humidity data WINTER TEMPERATURE water vapor concentrations are among the expected at 850 hPa level for the 41 yr from 1958 to WINTER AVERAGE EQUIVALENT climate changes due to variations in greenhouse gas 1998 from the National Centers for TEMPERATURE 1958-1998 TREND 1958-1998 concentrations (Kattenberg et al., 1995). However Environmental Prediction–National Center for both increments could be due to changes in the frecuencies of natural atmospheric circulation Atmospheric Research (NCEP–NCAR) regimes (Wallace et al. 1995; Corti et al. 1999). reanalysis. Changes in the long-wave patterns, dominant We calculated daily values of equivalent airmass types, strength or position of climatological “centers of action” should have important influences temperature for every grid point according to on local humidity and temperatures regimes. It is the expression in figure-1. The monthly, known that the recent upward trend in the NAO seasonal and annual means were constructed accounts for much of the observed regional warming from daily means. Seasons were defined as in Europe and cooling over the northwest Atlantic Winter (January, February and March), Hurrell (1995, 1996). However our knowledge about Spring (April, May and June), Summer (July, the influence of NAO on humidity distribution is very August and September) and Fall (October, limited. In the three recent global humidity November and December). -
Physiological Equivalent Temperature Index Applied
The seventh International Conference on Urban Climate, 29 June - 3 July 2009, Yokohama, Japan PHYSIOLOGICAL EQUIVALENT TEMPERATURE INDEX APPLIED TO WIND TUNNEL EROSION TECHNIQUE PICTURES FOR THE ASSESSMENT OF PEDESTRIAN THERMAL COMFORT Alessandra Rodrigues Prata-Shimomura; Leonardo Marques Monteiro; Anésia Barros Frota * *Laboratório de Conforto Ambiental e Eficiência Energética, Faculdade de Arquitetura e Urbanismo, Universidade de São Paulo - LABAUT/FAUUSP, São Paulo, Brazil Abstract The goal of this research was to verify the influence of the effect of the wind on the pedestrians and the applicability of an index of environmental comfort for external spaces, according to data of wind tunnel simulations. The simulations were performed for the case study of Moema, an upper middle class verticalized residential neighbourhood in Sao Paulo, Brazil. The index used was the Physiological Equivalent Temperature (PET), established specifically for the evaluation of subtropical climates such as the one from the study area. Figures obtained from wind tunnel simulations, using erosion techniques, were used to visualize the field of speed in the level of pedestrian, describing the areas affected by the action of different wind speeds The index was applied on the erosion technique pictures, defining the areas of greater and lesser influence in terms of the effect of wind on the climatic conditions of the site. As a result, one may verify the assessment of the area under study, observing the conditions of comfort and discomfort in light of changes in the values of wind speed. Key words: thermal comfort indices, urban external spaces, wind tunnel simulation 1. INTRODUCTION The metropolitan region of São Paulo has 20 million inhabitants, 11 million of which live within the capital’s boundaries, making it the largest urban agglomeration of South America (Brandão, 2007). -
Basic Features on a Skew-T Chart
Skew-T Analysis and Stability Indices to Diagnose Severe Thunderstorm Potential Mteor 417 – Iowa State University – Week 6 Bill Gallus Basic features on a skew-T chart Moist adiabat isotherm Mixing ratio line isobar Dry adiabat Parameters that can be determined on a skew-T chart • Mixing ratio (w)– read from dew point curve • Saturation mixing ratio (ws) – read from Temp curve • Rel. Humidity = w/ws More parameters • Vapor pressure (e) – go from dew point up an isotherm to 622mb and read off the mixing ratio (but treat it as mb instead of g/kg) • Saturation vapor pressure (es)– same as above but start at temperature instead of dew point • Wet Bulb Temperature (Tw)– lift air to saturation (take temperature up dry adiabat and dew point up mixing ratio line until they meet). Then go down a moist adiabat to the starting level • Wet Bulb Potential Temperature (θw) – same as Wet Bulb Temperature but keep descending moist adiabat to 1000 mb More parameters • Potential Temperature (θ) – go down dry adiabat from temperature to 1000 mb • Equivalent Temperature (TE) – lift air to saturation and keep lifting to upper troposphere where dry adiabats and moist adiabats become parallel. Then descend a dry adiabat to the starting level. • Equivalent Potential Temperature (θE) – same as above but descend to 1000 mb. Meaning of some parameters • Wet bulb temperature is the temperature air would be cooled to if if water was evaporated into it. Can be useful for forecasting rain/snow changeover if air is dry when precipitation starts as rain. Can also give -
Modeling of Heat Stress in Sows—Part 1: Establishment of the Prediction Model for the Equivalent Temperature Index of the Sows
animals Article Modeling of Heat Stress in Sows—Part 1: Establishment of the Prediction Model for the Equivalent Temperature Index of the Sows Mengbing Cao 1,2, Chao Zong 1,2,*, Xiaoshuai Wang 3, Guanghui Teng 1,2, Yanrong Zhuang 1,2 and Kaidong Lei 1,2 1 College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China; [email protected] (M.C.); [email protected] (G.T.); [email protected] (Y.Z.); [email protected] (K.L.) 2 Key Laboratory of Agricultural Engineering in Structure and Environment, Ministry of Agriculture and Rural Affairs, Beijing 100083, China 3 College of Biosystems Engineering and Food Science, Zhejiang University, No. 866 Yuhangtang Road, Hangzhou 310058, China; [email protected] * Correspondence: [email protected] Simple Summary: Sows are susceptible to heat stress. Various indicators can be found in the literature assessing the level of heat stress in pigs, but none of them is specific to assess the sows’ thermal condition. Moreover, previous thermal indices have been developed by considering only partial environment parameters, and the interaction between the index and the animal’s physiological response are not always included. Therefore, this study aims to develop and assess a new thermal index specified for sows, called equivalent temperature index for sows (ETIS), with a comprehensive consideration of the influencing factors. An experiment was conducted, and the experimental Citation: Cao, M.; Zong, C.; Wang, data was applied for model development and validation. The equivalent temperatures have been X.; Teng, G.; Zhuang, Y.; Lei, K. transformed on the basis of equal effects of air velocity, relative humidity, floor heat conduction and Modeling of Heat Stress in indoor radiation on the thermal index, and used for the ETIS combination. -
The Basis of Wind Chill RANDALL J
ARCTIC VOL. 48, NO. 4 (DECEMBER 1995) P. 372– 382 The Basis of Wind Chill RANDALL J. OSCZEVSKI1 (Received 21 June 1994; accepted in revised form 16 August 1995) ABSTRACT. The practical success of the wind chill index has often been vaguely attributed to the effect of wind on heat transfer from bare skin, usually the face. To test this theory, facial heat loss and the wind chill index were compared. The effect of wind speed on heat transfer from a thermal model of a head was investigated in a wind tunnel. When the thermal model was facing the wind, wind speed affected the heat transfer from its face in much the same manner as it would affect the heat transfer from a small cylinder, such as that used in the original wind chill experiments carried out in Antarctica fifty years ago. A mathematical model of heat transfer from the face was developed and compared to other models of wind chill. Skin temperatures calculated from the model were consistent with observations of frostbite and discomfort at a range of wind speeds and temperatures. The wind chill index was shown to be several times larger than the calculated heat transfer, but roughly proportional to it. Wind chill equivalent temperatures were recalculated on the basis of facial cooling. An equivalent temperature increment was derived to account for the effect of bright sunshine. Key words: bioclimatology, cold injuries, cold weather, convective heat transfer, face cooling, frostbite, heat loss, survival, wind chill RÉSUMÉ. La popularité de l’indice de refroidissement du vent a souvent été expliquée par le fait qu’on peut la relier plus ou moins à l’effet du vent sur le transfert thermique à partir de la peau nue, le plus souvent celle du visage. -
The First Law of Thermodynamics Continued Pre-Reading: §19.5 Where We Are
Lecture 7 The first law of thermodynamics continued Pre-reading: §19.5 Where we are The pressure p, volume V, and temperature T are related by an equation of state. For an ideal gas, pV = nRT = NkT For an ideal gas, the temperature T is is a direct measure of the average kinetic energy of its 3 3 molecules: KE = nRT = NkT tr 2 2 2 3kT 3RT and vrms = (v )av = = r m r M p Where we are We define the internal energy of a system: UKEPE=+∑∑ interaction Random chaotic between atoms motion & molecules For an ideal gas, f UNkT= 2 i.e. the internal energy depends only on its temperature Where we are By considering adding heat to a fixed volume of an ideal gas, we showed f f Q = Nk∆T = nR∆T 2 2 and so, from the definition of heat capacity Q = nC∆T f we have that C = R for any ideal gas. V 2 Change in internal energy: ∆U = nCV ∆T Heat capacity of an ideal gas Now consider adding heat to an ideal gas at constant pressure. By definition, Q = nCp∆T and W = p∆V = nR∆T So from ∆U = Q W − we get nCV ∆T = nCp∆T nR∆T − or Cp = CV + R It takes greater heat input to raise the temperature of a gas a given amount at constant pressure than constant volume YF §19.4 Ratio of heat capacities Look at the ratio of these heat capacities: we have f C = R V 2 and f + 2 C = C + R = R p V 2 so C p γ = > 1 CV 3 For a monatomic gas, CV = R 3 5 2 so Cp = R + R = R 2 2 C 5 R 5 and γ = p = 2 = =1.67 C 3 R 3 YF §19.4 V 2 Problem An ideal gas is enclosed in a cylinder which has a movable piston. -
Bulletin American Meteorological Society
BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY Entered as second class matter at the Post Office, Worcester, Massachusetts, under Act of Aug. 24, 1912. Issued monthly except July and August. Annual subscription, $3.00; single copies of this issue, 35c. Address all communications to ROBERT G. STONE, Editor Blue Hill Observatory, Harvard University Milton, Mass., U. S. A. Vol. 20 OCTOBER, 1939 No. 8 A Diagram for Obtaining in a Simple Manner Different Humidity Elements and its Use in Daily Synoptic Work DR. W. BLEEKER Subdirector, Royal Netherlands Meteorological Institute, De Bilt, Holland 1. DEFINITIONS AND SYMBOLS 2. CONSTRUCTION OF THE DIAGRAM T — Temperature. The relations between the tempera- Te — Equivalent temperature, the ture, T, the equivalent temperature, temperature which the air Te, and the wet-bulb temperature, Tw, would assume if all water va- are given by pour were condensed at con- (cp+tfcpw) (T-Tw)=Lw M), (1) stant pressure and the heat of condensation used to increase cP (Te-Tw) = Lw Xw, (2) the temperature of the air (von cP (T-Te)+xcPw (T-Tw) = -LwX. (3) Cpw Bezold, 1905). Since = about 2 and x seldom Tw = theoretical wet-bulb tempera- cP ture, the lowest temperature to exceeds 0.025 we may write: which the air can be cooled un- der constant pressure by evap- T-Tw - —— (x-xw), (la) cP orating water into the air -Lw (Normand, 1921; Brunt, 1934). Te-T w = ( Xe — X w ) , (2a) fw equals the temperature of a well-ventilated wet-bulb ther- T-Te = (X - Xe), (3a) mometer (Assmann-psychrome- Cp ter. -
Lecture Ch. 6 Condensed (Liquid) Water How Does Saturation Occur? Cloud in a Jar Demonstration Saturation of Moist Air Saturatio
Lecture Ch. 6 Condensed (Liquid) Water • Saturation of moist air • Ch. 4: Will H2O condense? • Relationship between humidity and dewpoint – Clausius-Clapeyron describes esat(T) – Clausius-Clapeyron equation • Ch. 5: What will H2O condense on? • Dewpoint – Kohler describes droplet formation – Temperature • Ch. 6: How much H2O will condense? – Depression – Dew point temperature provides metric • Isobaric cooling • Ch. 7: How does condensed H2O affect stability? • Moist adiabatic ascent of air – Conditional stability is affected by moist adiabats • Equivalent temperature • Ch. 8: What happens to condensed H2O? • Aerological diagrams – Precipitation processes Curry and Webster, Ch. 6 Cloud in a Jar Demonstration How does saturation occur? • By increasing water vapor – Evaporation of water at surface – Evaporation of falling rain http://www.youtube.com/ • By cooling watch?v=XH_M4jItiKw – Isobaric – Radiative cooling of rising air • By mixing of two unsaturated air parcels http://groups.physics.umn.edu/demo/old_page/demo_gifs/4B70_20.GIF Curry and Webster, Ch. 6 Saturation of Moist Air Saturation of Moist Air • Dew point temperature • Clausius-Clapeyron equation at dew point R T v = v v p dp L = lv dT p R T 2 € v Llv dln p = 2 dT RvT dln p L = lv dT R T 2 Curry and Webster, Ch. 6 v € 1 Clausius Clapeyron Dewpoint and Humidity • Recall by integration between two temperatures • Integrating from ambient to saturation! we had • Dew point depression (T-TD) 1.0 T=2C INCORRECT! T=24C Figure is wrong. T=46C 0.8 0.6 0.4 Relative Humidity 0.2 0.0 0 5 10 15 20 Dewpoint Depression (T-Td) Start with measured Equivalent Potential Temperature T and Td with altitude, then overlay ws(T). -
12/8 and 12/10/2010
PY105 C1 1. Help for Final exam has been posted on WebAssign. 2. The Final exam will be on Wednesday December 15th from 6-8 pm. First Law of Thermodynamics 3. You will take the exam in multiple rooms, divided as follows: SCI 107: Abbasi to Fasullo, as well as Khajah PHO 203: Flynn to Okuda, except for Khajah SCI B58: Ordonez to Zhang 1 2 Heat and Work done by a Gas Thermodynamics Initial: Consider a cylinder of ideal Thermodynamics is the study of systems involving gas at room temperature. Suppose the piston on top of energy in the form of heat and work. the cylinder is free to move vertically without friction. When the cylinder is placed in a container of hot water, heat Equilibrium: is transferred into the cylinder. Where does the heat energy go? Why does the volume increase? 3 4 The First Law of Thermodynamics The First Law of Thermodynamics The First Law is often written as: Some of the heat energy goes into raising the temperature of the gas (which is equivalent to raising the internal energy of the gas). The rest of it does work by raising the piston. ΔEQWint =− Conservation of energy leads to: QEW=Δ + int (the first law of thermodynamics) This form of the First Law says that the change in internal energy of a system is Q is the heat added to a system (or removed if it is negative) equal to the heat supplied to the system Eint is the internal energy of the system (the energy minus the work done by the system (usually associated with the motion of the atoms and/or molecules). -
Cooling Load Calculations and Principles
Cooling Load Calculations and Principles Course No: M06-004 Credit: 6 PDH A. Bhatia Continuing Education and Development, Inc. 22 Stonewall Court Woodcliff Lake, NJ 07677 P: (877) 322-5800 [email protected] HVAC COOLING LOAD CALCULATIONS AND PRINCIPLES TABLE OF CONTENTS 1.0 OBJECTIVE..................................................................................................................................................................................... 2 2.0 TERMINOLOGY ............................................................................................................................................................................. 2 3.0 SIZING YOUR AIR-CONDITIONING SYSTEM .......................................................................................................................... 4 3.1 HEATING LOAD V/S COOLING LOAD CALCULATIONS........................................................................................5 4.0 HEAT FLOW RATES...................................................................................................................................................................... 5 4.1 SPACE HEAT GAIN........................................................................................................................................................6 4.2 SPACE HEAT GAIN V/S COOLING LOAD (HEAT STORAGE EFFECT) .................................................................7 4.3 SPACE COOLING V/S COOLING LOAD (COIL)........................................................................................................8 -
17.Examples of the 1St Law Rev2.Nb
17. Examples of the First Law Introduction and Summary The First Law of Thermodynamics is basically a statement of Conservation of Energy. The total energy of a thermodynamic system is called the Internal Energy U. A system can have its Internal Energy changed (DU) in two major ways: (1) Heat Q > 0 can flow into the system from the surroundings, in which case the change in internal energy of the system increases: DU = Q. (2) The system can do work W > 0 on the surroundings, in which case the internal energy of the system decreases: DU = - W. Generally, the system interacts with the surroundings by exchanging both heat Q and doing work W, and the internal energy changes DU = Q - W This is the first law of thermodynamics and in it, W is the thermodynamic work done by the system on the surroundings. If the definition of mechanical work W were used instead of W, then the 1st Law would appear DU = Q + W because doing work on the system by the surroundings would increase the internal energy of the system DU = W. The 1st Law is simply the statement that the internal energy DU of a system can change in two ways: through heat Q absorption where, for example, the temperature changes, or by the system doing work -W, where a macroscopic parameter like volume changes. Below are some examples of using the 1st Law. The Work Done and the Heat Input During an Isobaric Expansion Suppose a gas is inside a cylinder that has a movable piston. The gas is in contact with a heat reservoir that is at a higher temperature than the gas so heat Q flows into the gas from the reservoir.