Pulsation andor vibration can cause metal fatigue and lead to failure of the heat exchanger. Steam is supplied in a gaseous state to the heat exchanger. If we select a steamtowater heat exchangeralso called a convertorat 30 psig entering steam pressure, we get a shorter unit than if we select it at 5. The following article demonstrates how to calculate and compare the u value for the heat transfer of steam and hot water through different types of. If the temperature drop of the hot water is not to exceed 15 c, how much tube length is. In contrast to the parallel flow heat exchanger, the counter flow heat exchanger can have the hottest coldfluid. Steam at a rate of 100 kgh is used to heat a stream of gas flowing on the tube side of a heat exchanger. If the heat exchanger is used in a pneumatic conveying system, a check valve should be placed between the air lock and the heat exchanger. Designing steps for a heat exchanger ijert journal. Boiler heat exchangers from bryan steam flexible water tube.
The pool water is heated as it passes through the copper indirect coil. The two most common heat exchanger design problems are those of rating and sizing. Fast and detailed cleaning of heat exchanger plates. Code to add this calci to your website just copy and paste the below code to your webpage where you want to display this calculator. If the condensate is allowed to discharge by gravity into a vented receiver 0 back pressure, a vacuum breaker will open, exposing the exchanger to atmosphere pressure. Heat exchanger effectiveness ntu method if more than one of the inlet and outlet temperature of the heat exchanger is unknown, lmtd may be obtained by trial and errors solution. The energy released when steam condenses to water is in the range 2000 2250 kjkg depending on the pressure compared to water with 80 120 kjkg with temperature difference 20 30 o c.
Producing hot water by direct steam injection final. This means that the plate heat exchanger can remain in service far longer between cleaning intervals. Water flows inside the inner pipe and steam flows through the annulus formed between the two pipes. Taco steam to liquid heat exchangers feature utube construction and are built in accordance with asme section viii. For an existing heat exchanger the geometry, flows and specific heats of the flows give the effectiveness. This pdf presentation is designed to highlight the. Overall heat transfer coefficient for doublepipe heat exchanger. May 03, 2000 under lowload conditions, or when the control valve is closed completely, a vacuum will form inside the heat exchanger as steam collapses to a much smaller volume of condensate. Tm is the log mean temperature difference given as t t. Table 1 properties of saturated steam heat exchanger selection the heat exchanger should be selected for operation at the minimum pressure to. Shell and tube heat exchangers basic calculations pdh online. Hot water or steam is taken from the heating main and circulated thru the utube heat exchanger shell.
Combining each of these resistances in series gives. A heat exchanger is an energy exchange system in the form of heat between a hot and a cold fluid. F correction factors for several heat exchanger types. The term heat exchanger applies to all equipment used to transfer heat between two streams. The overall heattransfer coefficient of the exchanger is 300 wm2 k, and the area for heat transfer is 15. In practice, all the thermal duty of the hot fluid fc is transferred to the cold fluid ff, thereby fulfilling the next energy balance. Heating with steam tlv a steam specialist company uk. Steam condensing rate for air heating equipment can be calculated as. Jan 16, 2017 the closer the shellside steam temperature is to the average tubeside water temperature, the longer the exchanger becomes and the more square feet of heat transfer surface is required. That is, the design of a two fluid heat exchanger used for the purposes of.
Equation 14 may vary from rough estimation to calculation based on the exchanger geometry. As post no 6 notes, steam tables can be more convenient than heat capacities. The term heat exchanger encompasses all devices used to transfer energy from one fluid to another. A wide variety of materials allows you to choose the configuration thats best for your particular application. The watertowater heat exchanger design differs from steam heat exchangers. Calculate the estimated heat transfer area required, using. The optimum heat transfer rate takes place in a balanced counter flow heat exchanger and by using this optimum rate of heat transfer, the concept of heat exchanger efficiency is introduced as the. As steam condenses in a heat exchanger, only the latent heat about 880 btus is released to heat the water.
Classification the more general classification that can be done for heat exchangersis. For example, a new heat exchanger designed for 15 psi steam to heat water to 160 degrees will generally heat the full system load with 0 psi steam in the heat exchanger shell. For a singlepass counterflow heat exchanger the design. Engineering calculator tlv a steam specialist company usa.
This same amount of heat is released when a pound of steam is condensed back into a pound of water. This will help to prevent clogging the heat exchanger with the product being conveyed. Heat exchangers or similar units for producing steam from water are often called boilers or steam generators. Why use low steam pressure steam heat exchanger basics part 2. Consider a parallelflow heat exchanger, which is used to cool oil from 70c to 40c using water available at 30c. Manufacturers of steam to water heat exchangers browse companies that make steam to water heat exchangers and view and download their free cad details, revit bim files, specifications and other content relating to steam to water heat exchangers as well as other product information formated for the architectural community. Manufacturers of steamtowater heat exchangers browse companies that make steamtowater heat exchangers and view and download their free cad details, revit bim files, specifications and other content relating to steamtowater heat exchangers as well as other product information formated for the architectural community. Some of the water evaporates and this fresh steam flows into the tube of the next stage. The sum of the heat of the liquid column 4 and latent heat column 5 in btu. Calculate the rate of heat transfer to the gas side. Counter flow heat exchangers are the most efficient of the three types. Chapter 5 heat exchangers faculty of engineering and.
Eliminates need for periodic, expensive chamber cleaning. The heat transfer analysis is done by considering water inside the tube and steam on shell side. Sep 26, 2017 definition of the process for the calculation of heat exchangers. Heat exchangers 73 individual thermal resistances of the system. Another approach introduce the definition of heat exchanger effectiveness, which is a dimensionless with ranging between 0 to1. Overall heat transfer coefficient for doublepipe heat. May 04, 2009 coefficient of the heat exchanger is 640 wm 2 k, determine the length of the heat exchanger required to achieve the desired heating. Liquid condensate exits the heat exchanger at close to saturated steam temperatures. Design and analysis of a newly installed plate heat. Pdhonline course m371 2 pdh shell and tube heat exchangers. Make an initial estimate of the overall heat transfer coefficient, u, based on the fluids involved. It is referred to as a laminar flow heat exchanger if the surface area density is above about 3000 m2m 3 914 ft2ft3, and as a micro heat exchanger if the surface area density is above about 10,000 m2m 3 3050 ft2ft3. Heat exchanger and its types engineering solutions.
Calculating mass of steam by energy balance process heat. Saturated steam at 100 psig, for example, contains 1,189 btus per pound. Overall heat transfer coefficient tlv a steam specialist. Estimate the pressure drop across the heat exchanger. Othe volume of water can be heated up very quickly othe system does not rely on stratification, it uses a continuous high flow pump to draw cold water from the tank through the heat exchanger and back to the tank, heating the water from cold to hot in a single pass othe secondary pressure drop is reduced to that of the vessel only. A quantity of water is heated with steam of 5 bar 72. In first stage feed water is heated by steam in tubes. Production and supply of every type of nut and pin. The steam enters the shell side of the heat exchanger as saturated vapor at 10 bar of 90% quality, and exits as saturated liquid water at 10 bar. Counterflow heat exchanger an overview sciencedirect. It is not unusual for the u value of a steam to water shell and tube heat exchanger for hydronic heating to be in the 500 to range before adding fouling. Heat flow steam side pail and scale heat flow water side rotameter.
Calculate the required heat transfer rate, q, in btuhr from specified information about fluid flow rates and temperatures. Heat exchangers jordan university of science and technology. Heat transfer with saturated steam utilizes the latent heat of steam, releasing a large amount of energy as it condenses changes to the liquid state. The exchange can take place between a process stream and a utility stream cold water, pressurized steam, etc, a process stream and a power source electric heat, or between two. The su heat exchanger is an instantaneous type, designed to heat liquids with steam. Since we dont do homework assignments for others, you should take it from here and work out the proper units and logic to arrive at the amount of saturated steam you need. Nov 22, 2017 this video describes how much steam is required to raise temperature of water to a certain degree in a heat exchanger. The experimental determination of heat transfer and. Delivery of heat exchanger operating like it is new. Kern shell side pressure drop correlations are based on 25% cut which is standard for liquid on shell side when steam or. A shell and tube heat exchanger used to heat water for space heating using either steam or water is often referred to as a nonstorage calorifier. But for better heat transfer, it is necessary to design a heat exchanger which fulfills the requirements of med unit. However, the term is commonly used to equipment in which two process streams exchange heat with each other.
Btus in the steam are actually used to heat the water. A benefit with steam is the large amount of heat energy that can be transferred. Institute utilizes a double pipe heat exchanger to facilitate the analysis and understanding of heat transfer inside a heat exchanger. Apr 18, 2016 the u value is the inverse of the resistance in the heat exchanger to heat transfer. Why use low steam pressure steam heat exchanger basics. Engineering calculator tlv a steam specialist company. The most common problems in heat exchanger design are rating and sizing. Although the su is used for heating many types of fluids, its widest application is for heating water.
Heat exchangers are used to transfer heat between two sources. In process calculations, the main objectives of heat exchanger calculations. The design of shell and tube heat exchanger using kern method for water and steam combination is validated by wellknown dittusboelter equation of turbulent flow inside tube. The u value is very dependent on the fluid type, the velocity, and the materials of construction. A quantity of water is heated with steam of 5 bar 6 bar abs from a temperature of 35 o c to 100 o c over a period of 20 minutes 1200 seconds. Calculate the amount of steam in the heat exchanger during the heat transfer with the given transfer rate and evaporation energy of steam.
The mass of water is 50 kg and the specific heat of water is 4. Cleaning heat exchanger plates with special chemicals. In fact, fouling has been recognised for a long time, and research on heat exchanger fouling was conducted as early as 1910 and the first practical application of this research was implemented in the 1920s. In contrast to the parallel flow heat exchanger, the counter flow heat exchanger can have the hottest coldfluid temperature greater than the coldest hotfluid temperatue. Steam control and condensate drainage for heat exchangers.
Twophase flow of liquid water and air in a plate gap has been studied by tribbe and. This pdf presentation is designed to highlight the features. Lmtd can be calculated by using the following formula, where. This heat quantity is different for every pressuretemperature combination, as shown in the steam table. The optimum thermal design of a shell and tube heat exchanger involves the.