University Course Series on Heat Exchanger Process Design – Practical Applications (Taught by Professor Wiseboy/Cheng Huiting)
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This post was last edited by wiseboy on 2022-12-14 at 13:29. Series of Practical Courses on Heat Exchanger Process Design – Summary. Lecturers: Wiseboy (UID:146194), Professor Cheng Huiting, the leading scientist at Xi’an Weiwei Chemical Software. Series of Practical Courses on Heat Exchanger Process Design (01): Heat Balance of Phase-Less Heat Exchangers (in this thread). Series of Practical Courses on Heat Exchanger Process Design (02): Effective Heat Transfer Temperature Difference. Series of Practical Courses on Heat Exchanger Process Design (03): Heat Transfer and Structural Calculations for Phase-Less Heat Exchangers – Structural Estimation. Series of Practical Courses on Heat Exchanger Process Design (04): Heat Transfer and Structural Calculations for Phase-Less Heat Exchangers – Calculation of Heat Transfer Coefficient. Series of Practical Courses on Heat Exchanger Process Design (05): Heat Transfer and Structural Calculations for Phase-Less Heat Exchangers – Calculation of Overall Heat Transfer Coefficient and Tube Length (Area). Series of Practical Courses on Heat Exchanger Process Design (06): Pressure Drop Calculation for Phase-Change Heat Exchangers. Series of Practical Courses on Heat Exchanger Process Design (07): Summary of Phase-Less Heat Exchangers. Series of Practical Courses on Heat Exchanger Process Design (08): The So-Called Wall Temperature. Series of Practical Courses on Heat Exchanger Process Design (09): Reference Materials – Software Calculation Results. Series of Practical Courses on Heat Exchanger Process Design (10): Process Design of Steam Condensation Heat Exchangers – Single-Component Condensation in the Shell Side. Series of Practical Courses on Heat Exchanger Process Design (11): Process Design of Steam Condensation Heat Exchangers – Multi-Component Condensation. Series of Practical Courses on Heat Exchanger Process Design (12): Process Design of Steam Condensation Heat Exchangers – Multi-Component Condensation with Inert Gases. Series of Practical Courses on Heat Exchanger Process Design (13): Process Design of Steam Condensation Heat Exchangers – Wiseboy’s Theory on Resistance and Film Thickness for Multi-Component Condensation with Inert Gases. Series of Practical Courses on Heat Exchanger Process Design (14): Process Design of Steam Condensation Heat Exchangers – Single-Component Condensation inside the Tubes. Series of Practical Courses on Heat Exchanger Process Design (15): Process Design of Steam Condensation Heat Exchangers – Errors in Condensation Film Coefficients and Their Impact on the Overall K Value. Series of Practical Courses on Heat Exchanger Process Design (16): Two Operating Conditions of Air Coolers (1) – Calculation of Condensate Water. Series of Practical Courses on Heat Exchanger Process Design (17): Two Operating Conditions of Air Coolers (2) – Calculation of Condensate Water. Series of Practical Courses on Heat Exchanger Process Design (18): Coiled Tubing Heat Exchangers – Thermal Calculations for Typical Heat Transfer Oil Heating Circulation Systems. Series of Practical Courses on Heat Exchanger Process Design (19): Coiled Tubing Heat Exchangers – Geometric Dimensions. Series of Practical Courses on Heat Exchanger Process Design (20): Coiled Tubing Heat Exchangers – Examples. Series of Practical Courses on Heat Exchanger Process Design (21): Combinations of Fluid Phases in Heat Exchangers. Series of Practical Courses on Heat Exchanger Process Design (22): Heat Transfer Efficiency of Heat Exchangers (1). Series of Practical Courses on Heat Exchanger Process Design (23): Fin-to-Tube Ratio and Calculation of Various Areas. Series of Practical Courses on Heat Exchanger Process Design (24): Box-Type Heat Exchangers (1) – Introduction. Series of Practical Courses on Heat Exchanger Process Design (25): Box-Type Heat Exchangers (2) – Example of a Typical Large-Scale Heat Exchanger. Series of Practical Courses on Heat Exchanger Process Design (26): Confusing Misconceptions – Temperature Cross-Over. Series of Practical Courses on Heat Exchanger Process Design (27): Examples of Heat Exchanger Design with Exit Temperature Cross-Over. Series of Practical Courses on Heat Exchanger Process Design (28): Exit Temperature Cross-Over – Finding a Solution – Spiral Plate Heat Exchangers. (To be continued…) __________________________________________________________________________ Preface From now on, I will focus on explaining heat exchanger process design here. Many long posts that required a lot of effort in the past have sunk to the bottom over time. From now on, I will try to gather my related posts here to facilitate communication and learning among everyone. This lecture focuses on tubular heat exchangers, while also covering other types of heat exchangers. Pay attention to the continuity between courses, as later courses are often related to those that came before. Some knowledge points will indicate the other basic knowledge or educational requirements needed to understand them, such as \"junior high school physics, junior high school math, university math, calculation methods (courses)\”; everyone should choose what to study based on their own situation. Try to provide manual calculation methods, but for those precise algorithms that are not suitable for manual calculation, solutions will be given. For some unresolved issues, approximate engineering solutions are also provided. If it were my own method, I would specify it clearly. Some *questions will provide the results of software calculations for comparison. **Much of the content in this lecture cannot be learned from university courses, training programs, textbooks, monographs, manuals, or standards. ** **This lecture is quite challenging and in-depth, with many secret weapons being revealed for the first time here. ** **It cannot fully suit the knowledge level of all readers. Take what you need and learn to be grateful. ** **Involves 4 major software packages with a wide range of applications: ** 1) Chinese THEM (Heat Exchanger Master Software) 【Cylindrical shells, fixed tube sheets, floating head type】 ； Trial version download: 2) Chinese VHeater (Coil Heat Exchange Doctor software) [Various types of coils] ； Trial version download: 3) Chinese BoxHeater (box-type heat exchanger software) 【Box/rectangular housing】 Trial version download: 4) Chinese and English SPHE (expert software for spiral plate heat exchangers) 【Spiral plate heat exchangers; the latest Chinese theory on spiral plate heat transfer】 Trial version download: Note: If reproducing this content, please indicate “Source: Haichuan Chemical Forum Wiseboy”. Acknowledgement: Some of the unique technologies come from the software heat exchanger series development materials provided by Xi’an Weiwei Computer Technology Co., Ltd., with permission granted for use. I would like to express my thanks here as well. ___________________________________________________________________________ Lesson 1: Heat Balance of the Formless Heat Exchanger I. Theoretical Part The heat exchange in a heat exchanger involves three types of heat: the heat absorbed by the fluid in the shell side, Qs; the heat released by the fluid in the tube side, Qt; and the heat released by the shell side to the environment, Qe. For phase-change-free heat transfer, the heat balance equation is: Qt = Qs + Qe. Qt = WtCpt(Tt1 – Tt2), Qs = WsCps(Ts2 – Ts1). To calculate Qe, parameters such as the entire structure of the heat exchanger and the fluid flow conditions are required, making the calculation complex; this will be discussed later. Approximately, by ignoring the heat loss Qe, the heat balance equation is: Qt = Qs, that is: WtCpt(Tt1 – Tt2) = WsCps(Ts2 – Ts1) (1-1). The red-colored parts represent the variables; there are 5 in total. If 4 of them are known, the value of the remaining one can be calculated. For example, knowing Tt1, Tt2, Ws, Ts2, Ts2, we can calculate Wt: Wt = Ws·Cps(Ts2 – Ts1) / (Tt1 – Tt2) (Equation 1-2). In this equation: W represents flow rate, in kg/S; T represents temperature, in C; CP represents specific heat, in J/(kg·C); s is an index indicating the shell side; t is an index indicating the tube side; 1 is an index indicating the inlet; 2 is an index indicating the outlet. Several key conclusions: 1. For the thermal balance of a heat exchanger, when heat losses are ignored, the heat balance depends only on process data and requirements, and not on the structure of the heat exchanger. 2. Formula (1-1) is from elementary algebra, and it can be understood with a junior high school education. II. *Question *Question 01-01: A water heater used in a medical system: Tube side: boiler water, inlet temperature of 80°C, outlet temperature of 60°C; Shell side: distilled water, flow rate of 0.1 kg/S; the lowest inlet temperature in winter is 10°C, and the outlet temperature is raised to 38°C. Ignoring heat losses, calculate the amount of boiler water and the heat required (without considering heat losses). Tip: Calculate using formula (1-2). Reference**: Wt=0.1400 kg/S, Q=0.1X4181(38-10)=11706.8 W; the source of property data can be found in Heat Exchanger Master:
Sofa~ Sit in the first row and study hard*:lol
This post was last edited by wiseboy on 2014-3-20 at 18:46. Lesson 2: Effective Heat Transfer Temperature Difference. I. Logarithmic Mean Temperature Difference △Tm: For counterflow: △T1=Tt1-Ts2, △T2=Tt2-Ts1; for co-flow: △T1=Tt1-Ts1, △T2=Tt2-Ts2. △Tm=（△T2-△T1）/ln（△T2/△T1). II. Effective Heat Transfer Temperature Difference △T1. Pure counterflow, co-current (without baffles), 1 tube side: △T=△Tm 2. Others △T=kf△Tm, where: kf is the temperature difference correction coefficient. It is important to note that when calculating heat exchangers, the effective heat transfer temperature difference △T is used. The formula for calculating the effective heat transfer temperature difference ΔT is quite complex; diagrams are available for reference. III. *Question *Question 02-01: In “*Question 01-01”, assuming that the heat exchanger has baffle plates or multiple tube passes, calculate the effective heat transfer temperature difference: Tt1=80°C, Tt2=60°C ； Ts1=10 C, Ts2=38 C ； Reference answer: △Tm=45.88 C, kf =0.9539 (calculated by Heat Exchanger Master; students can refer to the relevant chart or use the trial version by entering 4 temperatures). △T =43.77 C
Haha, thanks to the original poster for sharing so enthusiastically; you’ve worked hard
Thank you to the moderator for sharing. I would like to ask whether it is possible to calculate the value if the specific heat data is not available?
The physical property data of the mixture are, for the most part, calculated. As for how to calculate it, software is used almost entirely these days. Heat exchanger master can calculate some property data. In most heat exchanger designs these days, the thermodynamic simulations are carried out using process simulation software; the client provides the relevant simulation files or results, which include complete property data. Heat exchanger master can directly import property data from the simulation software Hysys. If you use Heat Exchanger Master, the provider will also provide you with a complete solution for the sources of material properties.
This post was last edited by wiseboy on 2014-3-21 21:06. Lesson 3: Heat transfer in formless heat exchangers – Structural calculations: Structural estimation. I. Rough estimation of the number of tubes: For liquids, the flow velocity Ut inside the tubes is limited to below 2.0 m/S. The flow area in the tube side can be estimated using the following formula: Ai = n(πdi²/4); the volumetric flow rate in the tube side is Vt = n(πdi²/4)Ut. Therefore, the number of tubes is given by: n = 4Vt/(πdi²Ut). Here, di represents the inner diameter of the tube, in meters； π —— Pi: 3.1416. When there are P tubes, the number of tubes is given by n = 4PVt/(πdi2Ut). II. Rough estimation of the shell diameter: This is a geometric problem and represents a complex part of the calculation; it involves estimating the inner diameter of the shell based on P tubes with an outer diameter of do. There are two methods: 1. If do refers to the commonly used heat exchange tubes: Φ19, Φ25, Φ38, you can refer to standards such as ”]B/T 4715 -92 Fixed-tube-sheet heat exchangers – Types and basic parameters”, and apply the corresponding shell diameter D and number of tubes n ； However, for pipes with a special outer diameter do, such as Φ9, there is no information available; the method described in “2” below must be used. ”. 2. By laying the pipes myself, I obtained similar values for n and D. Thus, the specific structure of a heat exchanger is determined. Only with a structure can its heat transfer coefficient K and area be calculated. III. *Question *Question 03-01: Based on the process parameters from *Question 01-01, the flow velocity inside the tubes is set at Ut=0.37 m/S. It is a fixed-tube-sheet heat exchanger; the heat exchange tubes are made of stainless steel with dimensions of Φ9.4X0.5. There are 2 tube banks, and the tube center distance is 12 mm, with the tubes arranged in an equilateral triangle pattern. The experiment provides a piping diagram for the heat exchanger, indicating the specific number of tubes, n, as well as the inner diameter of the shell, D. Reference answer: n = 4PVt/(πdi2Ut) = 4X2X(0.14/978)/(3.14X0.00842X0.37) ≈ 14. Important notes: 1. There are 18 tubes on the piping diagram, of which 4 are tie rods; only 14 are heat exchange tubes. 2. This is a water heater used in a certain medical system, and its heat exchange tubes are quite special: Φ9.4X0.5. If you try to apply some parameters from the petrochemical industry, you won’t find a match for them.
Thank you for the advice, and thanks as well for sharing.
Isn’t it necessary to perform another check after the heat exchanger’s structural design is completed? Check if it meets the process requirements? Is there enough margin?