2.2 Refrigerant Loop
Schematic of refrigerant-side loop in experimental facility is presented in Figure 3. Hot water used as heat transfer fluid enters the test heatexchanger at 35°C and is cooled by air flowing through louver fins across the condenser tubes in dry case tests. When wetting water was used a two-phase flow of air and wetting water cools the heat transfer fluid flowing through condenser tubes. Temperature of hot water was measured at inlet and outlet of test exchangerusing high precision PT 100 resistance temperature detector (RTD). Tap water was used as hot water fluid. Valve V2 provided water used for priming the centrifugal pump prior to start-up. A 0.75 kW VFD controlled centrifugal pump drives flow through hot-water loop which consists of a water filter placed before turbine flow meter. The desired temperature at test exchanger inlet was maintained usingheat supplied by a typical R-22 heat pump cycle using 4 kW fixed speed compressor, and a 4 kW auxiliary heater. Heat pump cycle was incorporated with a bypass valve between the compressor outlet and evaporator outlet, which enabled reducing the capacity of test heatexchanger condenser without changing the speed of the compressor by allowing certain amount of refrigerant to bypass from the compressor discharge line back to suction line. A 15 kW water chiller was utilized to cool overheated water and serves as additional temperature control along with bypass and temperature control valves.
Flattube corrugated multilouvered fins are used in many compact heatexchanger applications to enhance the air-side heat transfer performance. Louvers reduce the average thermal boundary -layer thickness by interrupting its growth and by enhancing mixing through large-scale instabilities, hence increasing the average heat transfer coefficient. Previous experimental and numerical studies have established that the heat transfer in multilouvered fins is influenced by three factors: a) duct versus louver directed flow [1,2]; b) thermal wake interference ; c) flow instabilities and transport of coherent vorticity in the vicinity of the louver surface . These three mechanisms have mostly been studied with a louver-centric view, i.e, heat transfer enhancement on a nominally two-dimensional louver, with the assumption that louvers contribute a significant portion to the overall heat transfer surface. For the most part this assumption is well justified. However, in exchangers with large fin pitches and small fin heights or tube pitch, the tube surface can contribute substantially to the total heat transfer. For example for a fin pitch of 1.5- 2.0 times the louver pitch, and a tube pitch of 5 louver pitches, the tube surface area contributes between 30 to 40 percent of the total heat transfer area. This, coupled with the fact that the tube is the primary heat transfer surface with the largest potential for heat transfer, requires that attention be paid to the heat transfer from the tube surface.
Du et al.  studied numerical Punched longitudinal vortex generators (LVGs) were employed to enhance air-side heat transfer on the wavy fin surface of flattube used in direct air-cooled condenser. The heat transfer enhancement of four types of the longitudinal vortex generators with different attack angles were compared by numerical simulations. It was found that the delta winglet pair with attack angle 25 could reach the greatest performance evaluation criteria (PEC) under the conditions of the inlet air flow velocity varied from 1 m/s to 5 m/s. The influences of locations on the wavy fin surface and the row number of the longitudinal vortex generators were also discussed. One delta winglet pairs at the middle of the wavy fin surface and the minimum row number, n = 1, with the average PEC is 1.23, had the best heat transfer performance of all conditions. as well as the numerical simulations verified that the delta winglet pairs can generate obvious longitudinal vortex pairs at the down-sweep zone, which can enhance the heat transfer between the cooling air flow and heated wall surface with acceptable pressure loss.
The principle advantage of U-Tubeheatexchanger (UTHX) is it’s less costly than floating head or packed floating head design heatexchanger. U-tube design allows for differential thermal expansion between the shell and tube bundle as well as for individual tubes. UTHX are capable of withstanding thermal shock applications. In UTHX, bundle can removed from one end for cleaning or replacement.
techniques which reduce the cooling load of buildings in summer season and this reduces the overall consumption of energy in a building. The ETHE control the ventilation air temperature using the thermal energy of the earth. Single pass earth-tubeheatexchanger (ETHE) was installed to study its performance in cooling mode. ETHE is made of 30 m long MS pipe of 0.073 m nominal diameter and 0.003 m wall thickness. ETHE is buried 3 m deep below surface. Ambient air is pumped through it by a 0.25 HP blower. Air velocity in the pipe is 6 m/s. Air temperature is measured at the inlet of the pipe and at the outlet (30 m), by thermocouple inserted into the pipe. Cooling tests were carried out for a period of one month (in the month of March). On each day system was operated for 6 hours during the day and shut down for the night. ETHE cools the ambient air in March by as much as 15 °C. Maximum COP obtained was 2.5. Basic theories of air conditioning were used to determine the selection parameters for blower.
To simulate the maldistribution, the quality distribution or liquid flow rate distribution among the parallel microchannel tubes have to be input into the model. Some previous studies have derived empirical distribution functions based on their experimental results. Vist (2003) applied the results of T-junction studies to develop a quality distribution function at the roundtube junction in the horizontal cylindrical header. Jin (2006) proposed a distribution function in the horizontal header by relating the branch tube quality with the ratio of vapor mass flux in the header immediately upstream to total inlet vapor mass flux. Watanabe et al. (1995) defined the liquid take-off ratio as the ratio of liquid mass flow rate in the branch tube to liquid mass flow rate in the vertical header immediately upstream. In annular flow, the liquid take-off ratio was constant. In froth or slug flow, the liquid take- off ratio was a function of vapor phase Reynolds number and liquid phase Weber number in the header immediately upstream. Vapor was considered as equally distributed among the tubes based on the measurement. Byun and Kim (2011) applied this approach to relate both vapor and liquid take-off ratio with vapor phase Reynolds number in the vertical header immediately upstream. With the wider range of test conditions and more fluids, Zou and Hrnjak (2013a, 2013b, 2015) found the inlet quality and liquid phase Froude number were also important parameters to liquid take-off ratio. Zou and Hrnjak (2015) generalized R134a and R410A distribution by relating the liquid take- off ratio with the header inlet quality as well as the vapor phase Reynolds number and liquid phase Froude number in the header immediately upstream.
To manufacture tube in tube type heatexchanger, tubes of SS and Cu are cut to required length. In this main task is to place Cu tube exactly concentric to SS tube, for which we have taken small disc of SS with hole at the centre with diameter equal to Cu tube outer diameter. Discs are welded at both the ends of SS tube by inserting Cu tube through it. To avoid any kind of leakage Small Grommets of required size are used. Over the time due to hot water flowing through copper tube grommet may wear, so for more protection to avoid water leakage sealing is provided with the use of proper sealing material which will not undergo any type of deformation or which will not form cracks in it over the time due to hot or cold water flow.
A shell and tubeheatexchanger is a class of heatexchanger designs. It is the most common type of heatexchanger in oil refineries and other large chemical processes, and is suited for higher-pressure applications. As its name implies, this type of heatexchanger consists of a shell (a large pressure vessel) with a bundle of tubes inside it. One fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids. The set of tubes is called a tube bundle, and may be composed of several types of tubes: plain, longitudinally finned, etc. Shell and tubeheatexchanger design is based on correlations between the Kern method and Bell-Delaware method, Moreover they are versatile and can be designed to suit for almost any application. Shell-and-tube exchangers are designed and fabricated according to the standards of the Tubular Exchanger Manufacturers Association (TEMA).  it is used for As process heat exchangers in the petroleum-refining and chemical industries, As steam generator, condensers, boiler feed water heater, and oil coolers in power plant.
Heatexchanger is a device to facilitate to exchange heat between two fluids without mixing at different temperature. In heatexchanger two modes of heat transfer occurs such as convection and conduction. Usually convection occurs in both working fluids and conduction through walls of heatexchanger which separates the fluids. Heat exchangers are used in a wide range of engineering applications, such as HVAC, aerospace industry and power generation. The main purpose of a heatexchanger is to efficiently transfer the heat from one fluid to the other. The performance of heatexchanger can be improved by improving the heat transfer between the heatexchanger fluids. There are so many ways to increase the heat transfer which include treated surfaces, rough surfaces, extended surfaces, surface vibration, and fluid vibration. The use of fins are recognized as one of the most effective means of increasing the heat dissipated. The objective of this study was to find out optimum type of fin arrangement used for maximum heat transfer rate. Experiments were conducted by varying the pitch. This task was performed by using CFD as a tool. CFD is a modeling technique that breaks down the governing equations (continuity, momentum and energy) for fluid flow into simpler forms that can be solved using numerical techniques. The mathematical resolution of the governing equations is still not fully resolved. CFD must then circumvent this by using models to approximate some components of the flow. This data acquiring from the different analysis is checked and choose the most effective way to increase heat transfer.
Tube side inlet / outlet nozzle Std., Schedule,Nos,ID,Type,Position For design case not required.
Impingement plate For design case not required.
If Shell side nozzle inlet / outlet RV2 is more than allowed limit then HTRI will consider Impingement plate. For gas & two phase flow Imp. Plate is required, For Liquid Phase it depends on RV2.Generally rectangular Imp. plate are used for Exchanger. There is some optional data, which is not required for design purpose. But this data Should be corrected at the time of rating & fine-tuning, which is given below.
every heat transfer applications. To make the heat exchangers less oversized its efficiency needed to be increased. In my experimental investigation effort has been made to increase the heat transfer rate from my heatexchanger in order to make the compact heat exchangers. For the secondary flow or swirling in fluid a twisted tape had been used with changing the twist ratio 2, 3 and 5. The flow velocities were varied from 0.5 to 2.5 l/min at a gap of 0.5. The result predicted that when the twisted tape is inserted it gives very high heat transfer rates if compared to a normal one. The annular cylindrical fins have been used on the outer periphery of the cylindrical tube. The increasing value of Reynolds number shows the increasing value of heat transfer rates.
ABSTRACT: Shell and tubeheatexchanger is the most common type heatexchanger widely used in oil refinery and other large chemical process, because it suits high pressure application. The objective of the paper is to study the different parameters affecting heat transfers of a shell and tubeheatexchanger and optimize the shell and tubeheatexchanger for maximum heat transfer using CFD analysis. Computational analysis mainly carried out in the case of baffle angle and tube arrangement. 5° baffle angle and 45° circular arrangement with 3 cm pitch show uniform tube arrangement and better heat transfer coefficient than other arrangements.
This study has been undertaken to study design and analysis of the shell and tubeheatexchanger. Shell and tubeheat exchangers are found to be a widely used heatexchanger in industry for heat exchange purpose. This study shows the effect of various parameters on shell and tube type heatexchanger such as heat transfercoefficient ,pressure drop , pitch layout and baffle spacing. Standard Design calculations are used to study the same. The study also shows the simulation work carried out using ‘Solidworks’ for Shell and tube type heatexchanger.
ABSTRACT: The heatexchanger is an important device in almost all of the mechanical industries as in case of process industries it is key element. Heat transfer augmentation techniques refer to different methods used to increase rate of heat transfer such as active, passive and compound technique. The present paper is a review of one of the passive augmentation techniques used in a concentric tubeheatexchangerusing inner wavy tube. The performance of counter flow heatexchanger will be studied with inner plain tube and inner wavy tube. Then this enhanced performance due to inner wavy tube will be compared with performance of heatexchanger with inner plain tube and percentage of enhancement will be calculated in different hot fluid temperature input and different mass flow rates of hot as well as cold water. Experimentally, Overall heat transfer enhancement will be studied and also, the experimental results will be validated with CFD simulation (FLUENT SOFTWARE).
exchanger were investigated experimentally ( Pahlavanzadeh H. et al., 2007) with water as working fluid. The heat transfer rate averagely increased by 22-28% for wire coil and 163 - 174% for wire mesh over a plain tube value depending on the type of tube insert, density of wire torsion and flow velocity. Pressure drop also increased substantially by 46% for wire coil and 500% for wire mesh. As Bogdan I. Pavel (Bogdan I. Pavel et al., 2004) carried out their work in a pipe with porous inserts in laminar and turbulent region with Reynolds number ranging from 1000-4500, the present work has been done similar lines but in turbulent region (Re number range of 7,000-14,000) as most of the flow problems in industrial heat exchangers involve turbulent flow region.
Abstract: Heatexchanger is a device used to transfer heat between one or more fluids. In this thesis, different nano fluids mixed with base fluid water are analyzed for their performance in the radiator. The nano fluids are Aluminum Oxide, Silicon Oxide and Titanium carbide for two volume fractions 0.7, 0.8. Theoretical calculations are done determine the properties for nano fluids and those properties are used as inputs for analysis.3D model of the shell and tubeheatexchanger is done in Pro/Engineer. CFD analysis is done on the shell and tubeheatexchanger for all nano fluids and volume fraction and thermal analysis is done in Ansys for two materials Aluminum and Copper for better fluid at better volume fraction from CFD analysis.
The heights of each section is fixed to a constant value. The area and height that is calculated for each section is the same. The heat flow varies for every section. The iterations are done until the pre-determined number of sections is reached, which determine the length of the heatexchanger. The inlet temperatures of the tube and shell are fixed before the simulation of the model starts. The flow is counter current. To start the iterations a guessed value of the outlet shell temperature is made. The guessed value provides the possibility to start the calculation at the same axial starting position. With the guessed outlet shell stream temperature the inlet shell stream temperature is determined. if it does not match the guessed value it is changed until the final value/ inlet shell stream temperature matches the pre-determined fixed value. This technique is based on the shooting method for numerical analysis. The explained theory is based on the hot shell and cold tube configuration. The hot tube and cold shell configuration has most of the same specifications, but differs in the heat balance. The heat is now transferred from the tube side to the shell side. The alternative formulas are depicted in equation (28), (29) and (30).
Abstract— A heatexchanger is a device, which transfer internal thermal energy between two or more fluids at different temperature. Without this essential piece of equipment most industrial process would be impossible. Heat exchangers are widely used in refrigeration air conditioning, and chemical plants. They can be employed in various uses, for instance, to effectively transmit heat from one fluid to the other. Shell-and-tubeheat exchangers (STHXs) are widely applied in various industrial fields such as petroleum refining, power generation and chemical process, etc. Tremendous efforts have been made to improve the performances on the tube side.In this project experimental performance is done on the fixed designed STHX and calculate the heat transfer coefficient and effectiveness. Validation is to be carried out using which gives the result comparison with that of experimental result.Here flow parameters are not varied but size and number of tubes are varied and best efficient model is selected as Optimized value. 3 different number of tubes are used with same shell size remaining same. 40 tubes , 32 tubes and 36 tubes were tried . It's been observed for same input temperatures and mass flow rates for three different models one with 36 tubes , 32 tubes model &other with 40 tubes, the temperature variation in 36 tubes is more and also requires less tubes compared to 40 tube model. so it is more effective than tubes model.
This paper provides heat transfer and friction factor data for single -phase flow in a shell and tubeheatexchanger fitted with a helical tape insert. In the double concentric tubeheatexchanger, hot air was passed through the inner tube while the cold water was flowed through the annulus. The influences of the helical insert on heat transfer rate and friction factor were studied for counter flow, and Nusselt numbers and friction factor obtained were compared with previous data (Dittus 1930, Petukhov 1970, Moody 1944) for axial flows in the plain tube. The flow was studied under laminar region. A maximum percentage gain of 165% in heat transfer rate is obtained for using the helical insert in comparison with the plain tube. It is due to the swirl flow motion provided by helical tapes.
Abstract: For the heat transfer to be large, the heat transfer area should be large. However by using nanofluids as the working fluid, the required heat transfer can be achieved by using the same apparatus. Current research suggests a promising future for graphite nanofluids. The main focus of this research ison developing higher convective heat transfer behavior of graphite nanofluids through the shell andtube heatexchanger under laminar flow.Graphite nanopowder is brought in the market and is dispersed in the base fluid (water) by varying its concentration such as 0.025%, 0.05%, 0.075%. The temperature of the hot and the cold fluid is noted down for each concentration. Keeping the flow rate of the hotter fluid as constant, flow rate of the colder fluid is varied. Also the effect of the flow rate and concentration on the heat transfer co-efficient has been discussed. It has been found that when the concentration of the graphite is increased, the heat transfer co-efficient increases gradually as the concentration increases.