Solved problems in psychrometry humidity air conditioning scribd. Two and a half cubic meters of lumber is being dried at 60c dry bulb temperature and 52c wet bulb temperature. Psychrometric chart fundamentals and its application to hvac troubleshooting by. The fastest and easiest method of evaluating psychrometric. From the psychrometric chart, we find the adiabatic saturation temperature of the air t s 28. Psychrometric chart problems practice exam questions. If a chart is not available for the particular atmospheric pressure desired, correction factors have to be applied to any solutions obtained from the available. A9, determine a the relative humidity, the humidity ratio, and the specific enthalpy of the mixture, in kj per kg of dry air, corresponding to drybulb and wetbulb temperatures of 30 and 25c, respectively. Furthermore, these errors decrease with decreasing pressure. However, numerical cal culation is practical only if the calculation method is computerized. All the types of problems related to the psychrometric chart are covered in this video, like problems on sensible heating, sensible cooling, humidification, dehumidification and on properties of.
In this work, we present a method for obtaining these properties from the multifluid mixture. Psychrometric chart fundamentals and its application to. It provides an invaluable aid in illustrating and diagnosing environmental problems such as why heated air can hold more moisture, and conversely, how allowing moist air to cool will result in condensation. Any question displayed here that is a follow on question may require information from a previous question. It consists of an inlet airwater vapor flow stream at temperature t 1, a liquid makeup. A psychrometric chart presents physical and thermal properties of moist air in a graphical form. Psychrometrics is the study of the thermodynamic properties of moist air. During this session, the psychrometric chart and its use in solving many air conditioning problems will be explained. Apr 08, 2017 all the types of problems related to the psychrometric chart are covered in this video, like problems on sensible heating, sensible cooling, humidification, dehumidification and on properties of. Let us see what these processes are and how they are represented on the psychrometric chart.
It provides an invaluable aid in illustrating and diagnosing environmental problems such as why heated air can hold more moisture, and conversely, how allowing moist air. With this knowledge, you will be able to understand many of the hvac challenges that are certain to arise, as well as anticipate problems before they occur, incorporating in your design. Solved problems in psychrometry free download as word doc. Sensible heat lost by the air is converted to latent heat in the added water vapor. Psychrometrics is the study of the air and water vapor mixture. Prior to the advent of the programmable calculator, the psychrometric chart was the most convenient method of solving psychrometric problems. Theory and application perry peralta nc state university. Using the psychrometric chart, the inlet air condition shows the humidity of the drying air to be 0. Using the psychrometric chart university of alabama. Use the psychrometric chart as a tool to determine the properties of.
Blackburn, pe, mba course content introduction if hvac problems and challenges are to be properly diagnosed and designed, it is essential that the psychrometric chart and psychrometrics in general be clearly understood. The course content is in a pdf file 522 kb psychrometric chart fundamentals and its application to hvac troubleshooting. Psychrometric charts can be pretty tricky to interpret. Through the dryer, the condition of the air follows a constant wetbulb line of about 27c, so at 35c its condition is a humidity of 0. Introduction the aim of this section of the notes is to allow students to size.
Psychrometrics is required to properly calculate heating and cooling loads, select equipment, and design air. The enthalpy can be found by using two triangles to draw a line parallel to the nearest enthalpy. Sensible cooling and sensible heating are basic psychrometric processes used for various applications. The psychrometric values were based on the oncoil and offcoil drybulb and wetbulb temperatures as indicated in the diagram. Psychrometrics problems humidity relative humidity. With so many lines and axes, you can get lost trying to follow the chart and find out which line represents which axis. The three methods are psychrometric tables, psychrometric charts, and the psychrometric calculator. Psychrometric charts allow you to track and monitor the physical and. Calculates heat required to raise temperature of saturated air and determines which of two systems has the lower wet bulb temperature. Thus, common fluids like waterair and common pipeduct materials are used. They are presented assuming the user to have a basic understanding of psychrometrics.
Solved problems in psychrometry humidity air conditioning. Principles of food and bioprocess engineering fs 231 solutions to example problems on psychrometrics 1. Psychrometric chart fundamentals and its application to hvac. Properties properties of each inlet stream are determined from the psychrometric chart fig. Just taking a look at it, you may already be confused. It can be very helpful in troubleshooting greenhouse or livestock building environmental problems and in determining solutions. Psychrometric properties of humid air are widely used in the analysis and modeling of thermal systems. Abe 201 extra practice problems extra psychrometry. It is defined as that index which collates the com binned effects of air temperature, relative humidity and air velocity on the human body. Pdf algorithms for the calculation of psychrometric. Psychrometric processes 1521 mechanical engineering me462562 sustainable energy.
Proficiency in the use of the psychrometric chart is an important tool for designers of air conditioning systems. We begin by identifying the conditions of the two streams on the psychrometric chart as follows. Problems with the low relative humidity resulting from simple heating can be eliminated by. Evaporative humidification processes normally occur without external heat transfer and are therefore adiabatic.
This chapter discusses perfect gas relations and describes their. The sensible cooling of air is the process in which only the sensible heat of the air is removed so as to reduce its temperature, and there is no change in the moisture content kgkg of dry air of. Uses of psychrometric chart the psychrometric chart conveys an amazing amount of information about air. For the first stream, the point on the psychrometric chart is obtained by following the. Introduction psychrometrics 2 the formulas that were developed were plotted on a chart that is the psychrometric chart.
Psychrometric chart fundamentals and its application. Psychrometrics quiz questions hvac certification practice tests. For psychrometric problems, use equations to solve this problem. Then, if possible, check your final answers using the psychrometric chart.
Psychrometric charts are designed for a given atmospheric pressure. Understanding psychrometric charts can help you visualize environmental control concepts, such as why heated air can hold. Whatever the type of coil, the air stream going through it can be plotted on the psychrometric chart, and important information learned about the air stream. Sample mechanical pe exam question on psychrometrics. Reading and interpreting a psychrometric chart sunbird dcim. Using the psychrometric chart problem statement the air in a oroom has a dry. The examples presented here, are for the purpose of familiarizing the user with the use of the program. Basic relationships most of the psychrometric equations that are used in practice are based on the premise that air is. An understanding of psychrometrics and use of the psychrometric chart is essential to the process of designing thermal systems and sizing the coils that are part of these systems.
Abe 201 extra practice problems extra psychrometry problems. So why is it important to know how to read a psychrometric chart. The solution to the problem is shown below to help the reader better understand the problem before it is solved in ees. What is the resulting mixed air dry bulb and wet bulb temperature. To view the question in context, click the link above the question to open up the exam in a new tab.
Understanding psychrometric charts helps visualization of environmental control concepts such as why heated air can hold. What is the final temperature of the conditioned air. Principles of food and bioprocess engineering fs 231. Feb, 2017 psychrometry nptel, psychrometry solved questions, psychrometric chart problems, psychrometry questions,psychrometric solved questions,psychrometric chart in hindi, psychrometric problems. If the outlet of an evaporative humidifier is saturated with water vapor. It provides an invaluable aid in illustrating and diagnosing environmental problems. This chart is one of the most useful tools a system designer has to describe air conditioning processes. It can be very helpful in troubleshooting and finding solutions to greenhouse or livestock building environmental problems. Gallos, the bastianblessing company introduction problems involving changes in temperature, humidity, and other properties of air can be solved by any of three methods. The psychrometric chart properties of air at first glance, the psychrometric chart appears to be an imposing network of lines. A simple adiabatic saturator is shown in figure 12.940 524 595 819 116 1575 1372 615 1564 857 468 499 457 791 1361 501 157 1495 1370 834 1436 729 1050 540 444 1255 1037 1457 1356 628 417 1400 363 68 181 383 1304 219 330 634 1001 373 309 437