The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. An arrangement of a heat exchanger where the hot and cold fluids enter at the opposite end and flow to the exit is known as counter flow. Lets take the case when we want to extract the maximum amount of heat from a given hot stream. The major types of heat exchanger include double pipe, shelltube, plate and shell, plate fin, and phase change heat exchangers. For example, refrigerators use heat exchangers to heat transfer from your groceries to the surrounding air. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural. Combining each of these resistances in series gives. In this type of device, the temperature difference between the two streams is kept to a minimum, because the hot source fluid on entering the heat exchanger is in closest contact to the sink fluid which is leaving the device, and vice versa. A first flow channel for a first medium is formed between the plates of each pair, and a second flow channel for the second medium is formed between adjacent pairs. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants. A schematic of a counterflow heat exchanger is shown in figure 18. Heattransfer characteristics of wet heat exchangers in. The paper gives an analytical dimensionless amalysis of local entropy generationand its ratio with local exchanded heat flow rate for parallel and counterflow heat exhangers. Logarithmic mean temperature difference chart pdf example arithmetic and logarithmic mean temperature, hot water heating air.
Crossflow, parallel flow, and counterflow heat exchanger configurations are three examples. Design and development of parallelcounter flow heat exchanger. Heat exchangers are typically classified according to flow arrangement and type of construction. T e temperature difference between hot and cold fluid at exit of heat exchanger a. Arithmetic mean temperature difference can be calculated as. Why is a counter flow heat exchanger better than a. Determine the length of the exchanger if the inner pipe has a 50 mm diameter and the overall heat transfer coefficient is u wm2k. Experimental study on parallel and counter flow configuration of a. Why is a counter flow heat exchanger better than a parallel. Full text of heat transfer in counterflow parallel flow and cross flow see other formats. A detailed analysis of this type of heat exchanger is therefore necessary. A heat exchanger can have several different flow patterns. Difference in counter heat exchanger and parallel flow heat.
There are probably heat exchanger in your office building which heat transfer from hot water to the ventilation. Calculate the total conductance of the heat exchanger. The main difference is that the tubeside fluid enters the exchanger at the opposite end of the shellside fluid. A counter flow or countercurrent shell and tube heat exchangers construction is in many ways identical to that of a parallel flow shell and tube heat exchanger. Experimental study on parallel and counter flow configuration. Pdf heat exchangers are used widely in many industries for heat recovery or cooling purposes. Use buttons to select either parallel or counterflow. Use engineering principles to support your premise. Mar 12, 2018 counter flow shell and tube heat exchangers. Effectiveness and efficiency analysis of parallel flow and.
Heat exchangers 73 individual thermal resistances of the system. The overall heat transfer coefficient u is constant throughout the heat energy. Cross flow heat exchanger provide compact design of heat exchanger. Derive the expression for log mean temperature difference. Whats the difference between parallel flow, counter flow and. Note that in a counterflow heat exchanger the outlet temperature of the cold fluid can exceed the outlet temperature of the hot fluid but this cannot happen in a parallel flow system. There is no loss of heat to the surroundings, due to heat exchanger being perfectly. In this work, heat transfer coefficients of shell and helically coiled tube heat exchanger using al 2 o 3 water nanofluid were studied. T i temperature difference between hot and cold fluid at inlet of heat exchanger. The heating is to be accomplished by passing hot engine. It can be operated as a parallel flow or as a counterflow heat exchanger. Comparison of heat exchanger types parallel heat exchanger.
Temperature profiles in a counter flow and b parallel flow single pass heat exchangers. Pdf heat exchanger lab experiment chemical engineering. Heat exchanger efficiency 4 has also been defined on the basis of efficiency of a fin of a constant area with its tip insulated, as a a f tanhf 3 where f a is the heat exchanger number and is expressed as, 2 ntu1 r f a for counter flow heat exchanger fand for parallel flow 2 ntu1 r a where ntu is the number of transfer units. For very high values of the conductance ratios, the heat exchanger will not perform as expected and both fluid temperatures will approach that of the ambient. Parallel flow and counter flow heat exchangers mcqs with. Other articles where parallelflow heat exchanger is discussed. Full text of heat transfer in counterflow parallel flow and. However, cross flow arrangement is commonly used because it is easier to provide inlet and outlet header connections with cross flow rather than counter flow. In counter flow heat exchangers the fluids enter the exchanger from. Full text of heat transfer in counterflow parallel flow. In this work, heat transfer coefficients of shell and helically coiled tube heat exchanger using al2o3 water nanofluid were studied.
A counterflow heat exchanger will require less heat exchange surface area than a parallel flow heat exchanger for the same heat transfer rate and the same inlet and outlet temperatures for the fluids. Analysis of a counter flow parallelplate heat exchanger asee. The inlet temperature of cooled fluid has insignificant impact on heat exchanger effectiveness. The temperature change of the hot fluid is a negative quantity, and so a negativesign is added to.
If the overall heat transfer coefficient is expected to be 1. This will still cool the hot fluid down by a considerable amount but is not as efficient as the counter flow system. Experiment regarding heat exchanger concurrentcountercurrent flows at same rate and different rates. The process of finding the heat transfer rate, heat transfer coefficients, lmtd and effectiveness of heat exchanger for both parallel and counter flow heat exchanger has been discussed. Parallel flow and counterflow heat exchangers are often compared. Plate heat exchanger, how it works working principle hvac industrial engineering phx heat transfer duration. Select temperature plot to show a plot of temperature versus distance through the heat exchanger for each stream. But of the three, the counter flow heat exchanger design is the most efficient when comparing heat transfer rate per unit surface area. Parallel and counter flow designs heat exchangers although ordinary heat exchangers may be extremely different in design and construction and may be of the single or twophase type, their modes of operation and effectiveness are largely determined. Parallel and counter flow designs heat exchangers although ordinary heat exchangers may be extremely different in design and construction and may be of the single or twophase type, their modes of operation and effectiveness are largely determined by the direction of the fluid flow within the exchanger. Heat exchanger transfer thermal energy from one medium to another. When two fluids flow in the same direction, it is referred to as a parallel flow type. Parallelflow heat exchangers with ambient thermal interaction.
Heat transferheat exchangers wikibooks, open books for an. The parallel flow arrangement is compared to counterflow and is found to be less effective under the external heat transfer condition. A more efficient design is the counter flow heat exchanger where the fluids flow through the heat exchanger in opposite directions. Ideal reversible heat transfer can be approached in a counterflow heat exchanger. A counterflow, concentric tube heat exchanger is designed to heat water from 20 to 80 degree c using hot oil, which is supplied to the annulus at 160 degree c and discharged at 140 degree c. Double pipe heat exchanger design with counterflow or. Counterflow heat exchanger an overview sciencedirect. However ordinary heat exchangers might be extremely dissimilar in design and construction and might be of the single or twophase kind, their modes of operation and efficiency are largely established by the direction of the fluid flow inside the exchanger. Heat exchangers are used in both cooling and heating processes. This paper developed a numerical model to simulate a. Che245 lab report solteq concentric tube heat exchanger. There are probably heat exchanger in your office building which heat transfer from hot water to the ventilation system in the winter and from the indoor air to the. The flow in a heat exchanger can be arranged as parallel flow, counter flow, and cross flow. A double pipe heat exchanger consists of one pipe inside another.
Difference in counter and parallel flow heat exchanger. Difference in counter heat exchanger and parallel flow. This will still cool the hot fluid down by a considerable amount but is not as. The wet heat exchanger has a higher effectiveness in counter flow than parallel flow. Experimental investigation of parallel and counter flow heat. Asee 2014 zone i conference, april 35, 2014, university. Lets assume we have a perfectly efficient, infinitely long heat exchanger with the same substance on each side, but one enters at 100 f and the other at 0 f. Shellandtube heat exchanger one shell shellandtube heat exchanger multiple shells crossflow heat exchanger unmixedunmixed crossflow heat exchanger mixedunmixed solid curves. The simplest heat exchanger is one for which the hot and cold fluids move in the same or opposite directions. Multipass cross flow heat exchanger can be easily manufactured compare to parallel and counter flow heat exchanger. Counterflow heat exchanger an overview sciencedirect topics. Why counter flow heat exchangers are more efficient. Pdf design and development of parallel counter flow.
Che245 lab report solteq concentric tube heat exchanger unit he. What is parallelflow and counterflow heat exchanger. Heat exchangers are classified by the flow pattern used to exchange hot and cold. In parallel flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. The temperatures of the hot stream and the cold stream of the heat exchanger are calculated from these differential equations for parallel flow. Presume that the exit temperature of water is not to. Parallel, counter, or cross flow of hot and cold streams. In a counterflow or countercurrent heat exchanger, hot and cold fluids enter the exchanger from opposite sides. Heat transfer l32 p2 temperatures for parallel and. Heat is transferred from the warm fluid through the wall of the inner tube the socalled heating surface to the cold fluid. This study was done by changing the parallel flow configuration into counter flow configuration under laminar flow regime. Temperature profiles in a counterflow and b parallel flow single pass heat exchangers. Note that in a counter flow heat exchanger the outlet temperature of the cold fluid can exceed the outlet temperature of the hot fluid but this cannot happen in a parallel flow system.
Double pipe heat exchanger design requires use of the heat transfer rate, the log mean temperature difference, and an estimate of the overall heat transfer coefficient to calculate the estimated heat transfer surface area. Pdf design and development of parallel counter flow heat. For shellandtube heat exchanger with multiple shell passes, it is assumed that the total ntuis equally distributed between shell passes of the same arrangement for crossflow heat exchangers, both fluids unmixed, eqn. On the diagram above they both flow from right to left. Dec 01, 2015 plate heat exchanger, how it works working principle hvac industrial engineering phx heat transfer duration. Innovations for the manufacture of industrial heat exchangers. New heat exchangers have been designed for emerging thermal. Select diagram to show a schematic of the heat exchanger. Parallel flow and counter flow heat exchangers mcqs with answers 1. Comparison of heat exchanger types each of the three types of heat exchangers parallel, cross and counter flow has advantages and disadvantages.
A heat exchanger can also be operated in counterflow, in which the two fluids flow in parallel but opposite directions. This heat exchanger consists of two concentric pipes of different diameters. The specific heats c p and mass flow rates of both fluids is constant. Be sure of keeping the steady water flow rate and temperature before noting down the readings to get accurate results. How is the logarithmic mean temperature difference lmtd calculated for heat exchangers.
The parallelflow arrangement is compared to counterflow and is found to be less effective under the external heat transfer condition. Can you remove transfer the same amount of heat from both heat exchangers. The basic component of a heat exchanger can be viewed as a tube with one fluid running through it and another fluid flowing by on the outside. Parallelflow heat exchanger counterflow heat exchanger. Apr 30, 2018 4b engineers whtsapp group for 2020,2021,2022 pass out students 4b engineers whtsapp group 2019 pass out stu. A heat exchanger for counterflow and parallel flow is comprised of a plurality of stacks of formstamped individual plates that are combined to pairs and the pairs are assembled atop one another to form the stacks. The answer to this is rooted in experiment, but it can be motivated by considering heat flow along a bar between two heat reservoirs at t a, t b as shown in figure 2. Pdf analysis of a counter flow parallelplate heat exchanger. That is, the rate of heat loss from the hot fluid at any section of a heat exchanger is equal to the rate of heat gain by the cold fluid in that section.
A heat exchanger is a system used to transfer heat between two or more fluids. The present work is directed towards the modeling of shell and tube parallel flow heat exchanger in solid works 2014 and setting up of flow simulation in solid works by inserting boundary. Set the length of the heat exchanger and the mass flow rates of the hot and cold fluids with sliders. There is no change of phase either of the fluid during the heat transfer. The two most common heat exchanger design problems are those of rating and sizing. The thinwalled inner tube has a diameter of di 20 mm, and. Hot water at 80 o c heats air from from a temperature of 0 o c to 20 o c in a parallel flow heat exchanger. Chapter 7 comparison of heat exchangers heat exchangers may be classified according to their flow arrangement. Parallel and counter flow designs heat exchangers engineers. Pdf local entropy production of the parallel flow and. Parallel flow heat exchanger in a parallel flow setup, both the hot fluid and cold fluids are travelling in the same direction as each other.
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