Welded plates expand the limits of plate heat exchangers. A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. Introduction to heat exchangers bengt sunden lund institute of technology. 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. But of the three, the counter flow heat exchanger design is the most efficient when comparing heat transfer rate per unit surface area.
The greater the temperature difference, the smaller will be the required heat transfer surface. Counter flow parallel flow cross flow split flow divided flow extended surface crosscounter flow. The heat exchanger is a device which transferred the. It is called a doublepipe exchanger because one fluid flows inside a pipe and the other fluid flows between that pipe and another pipe that surrounds the first. Heat exchanger transfer thermal energy from one medium to another. Tm is the log mean temperature difference given as t t. 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.
Heat exchangers are used in both cooling and heating processes. Another approach introduce the definition of heat exchanger effectiveness, which is a dimensionless with ranging between 0 to1. Why counter flow heat exchangers are more efficient. Asee 2014 zone i conference, april 35, 2014, university.
Pdf design and development of parallel counter flow. R sekulib university of kentucky introduction a heat exchanger is a device that is used for transfer of thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a. Improve sustainability with the champion of heat exchange. The heat exchanger must be isolated from system vibrations using flexible piping connections and isolation pads on the mounting feet. A heat exchanger typically involves two flowing fluids separated by a solid wall. If the heat exchanger is located at the inlet or discharge of a blower with a pulsating flow, such as a roots type rotary lobe blower, the heat exchanger must be protected from the pulsation by a chambered silencer. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural.
On the diagram above the cold fluid, highlighted in blue, is travelling right to left where as the warm fluid, shown in red and amber, travels left to right. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas processing and. It provides optimum heat transfer and flow conditions for a wide variety of fluids, with a builtin selfcleaning effect, while keeping the overall size of the unit to a. Heat exchanger design handbook by t kuppan free download. Model aca is designed with a floating rearread more. Mcadams was one of the earliest workers to quantitatively demonstrate this. The oil provides an average convection coefficient ho 400 wm2k on the outside of the tubes. Temperature difference leads to heat transfer and heat transfer changes the temperature difference. In the counter flow setup, the fluids are travelling along the heat exchanger in opposite directions. This paper developed a numerical model to simulate a counter flow parallel heat exchanger. Although the helical passages increase the heat transfer and reduce the size of the device, 3d print build constraints mandate that the passages are constructed with a lean angle for structural support that also increases. A heat exchanger is a device that is used to transfer thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid.
Heat exchanger effectiveness 2274 1 the effectiveness of a given heat exchanger can be defined as for cold stream c and hot stream h comparing the actual heat transfer with the maximum possible for the given geometry and material flows. The temperature differential is nowhere near as high as at the start of the parallel heat exchanger. Naik and matawala et al studied design and assessment of counter flow shell and tube heat exchangerby entropy generation minimization method. The results of heat transfer experiments show that the shellside heat transfer coefficient of the improved heat exchanger increased by 18. In parallel flow, both the hot and cold fluids enter the heat exchanger at the same end and move in the same direction, as shown in figure 1. A heat exchanger is a device that is used to transfer thermal energy enthalpy between two or more fluids, between a solid surface and a fluid. The heat transfer performance of a heat exchanger is the product of. Temperature profiles in a counterflow and b parallel flow single pass heat exchangers. In the heat exchanger, this effect is used to subcool the refrigerant liquid. A counter flow or countercurrent shell and tube heat exchanger s construction is in many ways identical to that of a parallel flow shell and tube heat exchanger. Counterflow heat exchanger an overview sciencedirect. 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. This means that the plate heat exchanger can also be dismantled for.
Heat leaves the warmer body or the hottest fluid, as long as there is a temperature difference, and will be transferred to the cold medium. A heat exchanger can have several different flow patterns. Water chilling in a counter flow heat exchanger in a counter flow heat exchanger, water is being chilled by sodium chloride brine. The counter flow design is most efficient, in that it can transfer the most heat from the heat transfer medium.
Counter flow parallel flow cross flow split flow divided flow extended surface cross counter flow. With reference to the vdi 6022, the cleaning of the components has to be done including the core cleaning pressure. 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. Difference in counter heat exchanger and parallel flow. Alfa laval compabloc heat exchangers combine superior efficiency with unmatched reliability. Make an initial estimate of the overall heat transfer coefficient, u, based on the fluids involved. Counter flow heat exchangers are the most efficient of the three types. 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 process streams resulting in energy integration and reduction of external heat sources. Comparison of heat exchanger types each of the three types of heat exchangers parallel, cross and counter flow has advantages and disadvantages. Fixed tubesheet exchanger nonremovable tube bundle. Heat is first transferred from the hot fluid to the wall by convection, 716 introduction to thermodynamics and heat transfer figure 164 the schematic of a shellandtube heat exchanger oneshell pass and onetube pass. 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. The simplest heat exchanger is one for which the hot and cold fluids move in the same or opposite directions. Difference in counter and parallel flow heat exchanger.
A shellandtube heat exchanger must be designed to heat 2. Che245 lab report solteq concentric tube heat exchanger unit he. 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. If the overall heat transfer coefficient of the heat exchanger is 640 wm 2 k, determine the length of the heat exchanger required to achieve the desired heating. Whats the difference between parallel flow, counter flow. Heat exchangers are used to transfer heat between two sources. This means that as the hot fluid enters from the right, it cools against the already warmed up cold fluid from the left. The stack of heat transfer plates and gaskets is clamped together with bolts in a frame. Make an initial estimate of the overall heat transfer coefficient, u, based on. Depending on the application polar recommends that a ther mostat be added to the heat exchanger to either prevent wa ter flowing. While as expected the fouled heat exchanger had a lower performance and therefore cooled the working fluid less, the performance of the counter heat exchanger unexpectedly of the parallel heat exchanger. Shellandtube heat exchangers funke warmeaustauscher.
Experiment regarding heat exchanger concurrentcountercurrent flows at same rate and different rates. Features and benefits full size air connections for reduced pressure drop and easy removal of condensed water. 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. Heat exchanger counterflow plate heat exchanger enthalpy counterflow plate heat exchanger rotary heat exchanger winter savings, kw 6,6. Counterflow heat exchanger energy recovery with eri. Effectiveness and efficiency analysis of parallel flow and.
A 2shell passes and 4tube passes heat exchanger is used to heat. For example, refrigerators use heat exchangers to heat transfer from your groceries to the surrounding air. Heat exchangers are typically classified according to flow arrangement and type of construction. A piece of equipment built for efficient heat transfer from one medium to another. Cfd analysis and performance of parallel and counter flow. 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. Within this type of heat exchanger, several layers of tubes are helically wound around a large centre tube, known as a mandrel. 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. A heat exchanger is a system used to transfer heat between two or more fluids. Two types of flow arrangement are possible in a doublepipe heat exchanger.
Heat exchangers 73 individual thermal resistances of the system. Crossflow, parallel flow, and counterflow heat exchanger configurations are three examples. Pdf heat exchanger lab experiment chemical engineering. Counter flow heat exchanger in counter flow heat exchangers the fluids enter the exchanger from opposite ends. This heat exchanger consists of two concentric pipes of different diameters. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. How lmtd of counter flow heat exchanger is greater than. Take a single pass shell and tube exchanger and look at how the temperature changes as we go along the length of it in small segments. The overall heat transfer coefficient of the exchanger is 300 wm2 k, and the area for heat transfer is 15. Calculate the required heat transfer rate, q, in btuhr from specified information about fluid flow rates and temperatures. The main difference is that the tubeside fluid enters the exchanger at.