Analysis of Thermodynamic Processes with Full Consideration of Real Gas Behaviour

Analysis of thermodynamic processes with full consideration of real gas behaviour

Version 2.12. - (July 2020)

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• What is TDT ?

• How does it look like ?

• How does it work ?

• Examples

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What is TDT ?

TDT is a Thermodynamic Design Tool, that supports the design and calculation of energetic processes on a 1D thermodynamic approach.

The software TDT can be run on Windows operating systems (Windows 7 and higher) or on different LINUX-platforms.

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© by B&B-AGEMA, No. 3 TDT - Features TDT - Features 1. High calculation accuracy: • real gas properties are considered on thermodynamic calculations • change of state in each component is divided into 100 steps

2. Superior user interface: • ease of input: dialogs on graphic screen • visualized output: graphic system overview, thermodynamic graphs, digital data in tables

3. Applicable various kinds of fluids: • liquid, gas, steam (incl. superheated, super critical point), two-phase state • currently 29 different fluids • user defined fluid mixtures

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Initial window after program start:  start a “New project”,  “Open” an existing project,  open one of the “Examples”, which are part of the installation, or  open the “Manual”.

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tree structure action toolbar

notebook containing overview and graphs

calculation output

On the left hand side of the window the entire project information is listed in a tree structure. The right hand side has three areas: the action toolbar (with buttons to start calculations), the notebook (containing the overview, graphs and diagrams) and the calculation output at the bottom.

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Currently, 9 different types of components are available in TDT:

. Compressor: component to increase the pressure of a compressible fluid

. Pump: component to increase the pressure of an incompressible fluid . Turbine: component to expand either compressible or incompressible fluids; this component also covers so-called expanders . Combustor: component to calculated simple combustion of gases

. Condenser: cools a fluid, so that liquid state is reached at the outlet

. Heat exchanger: general component to put heat into the fluid or to cool a fluid

. Pressure loss element: component to consider pressure losses e.g. in pipes

. Process branch: splitting and mixing of fluid flows

. Interface: used to create a connection between 2 heat exchangers

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© by B&B-AGEMA, No. 9 TDT - Available Fluids Applicable various kinds of fluids The current version of TDT2 can calculate the properties of 29 different fluids in the liquid, gas (super-heated and super-critical) and two-phase state.

◦ pure fluids: ◦ alkanes:

 Air (as a pure fluid)  Methane (CH4)  Water (H2O)  Ethane (C2H6)  Steam (H2O)  Propane (C3H8)  Carbon monoxide (CO)  Butane (C4H10)  Carbon dioxide (CO2)  Isobutane (C4H10)  Hydrogen (H2)  Pentane (C5H12)  Oxygen (O2)  Hexane (C6H14)  Nitrogen (N2) ◦ aromatic hydrocarbons:  Ammonia (NH3)  Toluene (C7H8) ◦ inert gases: ◦ refrigerants:

 Helium (He)  R11 (Trichlorofluoromethane, CCl3F)  Neon (Ne)  R12 (Dichlorodifluoromethane, CCl2F2)  Argon (Ar)  R123 (Dichlorotrifluoromethylmethane, C2HCl2F3)  Krypton (Kr)  R1234YF (Tetrafluoropropylene, C3H2F4)  Xenon (Xe)  R134 (Tetrafluoroethane, CH2FCF3)  R245CA (Pentafluoropropane, C3H3F5)  R245FA (Pentafluoropropane, C3H3F5)

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Definition of mixtures available, e.g.: • furnace gases • alkane mixtures • special gas compositions Fluids are defined by selecting components and assigning volume or mass fractions and additional humidity.

3 fluid mixture types: • Dry mixtures: no water content • Humid mixtures: water content, with condensation calculation • General mixtures: water allowed, no condensation is calculated

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Critical point

Various states possible in TDT: ・liquid ・vapor (super-heated, super-critical) ・two-phase state

Calculation of change of state v  p  Isentropic volume coefficient: k v     (compression & expansion) p  v s

n 1 n  v  1 Polytropic head: y  Z RT v  n v 1 Isentropic temperature coefficient: k  p 1 1 n 1 T p   v   1 T  T  ps nT 1 n T n 1 k 1 1 p k 1 Outlet temperature: T2  T1 Polytropic volume coefficient: v  v  T n v k v p k T

n 1 ZR 1   k 1 with pressure ratio , real gas coefficient Z, Polytropic temperature coefficient: T   p   T n c    k specific heat cp and polytropic efficiency p T p  p  T

Reference: K. H. Lüdtke: “Process Centrifugal Compressors – Basics, Function, Operation, Design, Application”, Springer-Verlag Berlin Heidelberg, Germany, 2004

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• change of state in each component is divided into several steps • real gas properties determined in each step

Entropy Differences of a Real and Isenthalpic Change of State**

** D. Bohn/H.E. Gallus , Energy Conversion Machinery engineering your visions

© by B&B-AGEMA, No. 14 TDT - Visualized Output . Thermodynamic diagrams • h-s diagram: Enthalpy over Entropy • p-s diagram: Pressure over Entropy • T-s diagram: Temperature over Entropy • p-h diagram: Pressure over Enthalpy • p-T diagram: Pressure over Temperature

. Q-T diagrams • Evaluation of heat transfer in interfaces • Inlet & outlet temperatures • Pinch point determination

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. 29 fluids (e.g. air, steam, CO2, hydrogen, helium, argon, methane, ethane, refrigerants) . Consideration of changing properties during compression / expansion . Export of properties into tables . User-defined fluid mixtures

 Implemented components  Compressor Heat exchanger  Pump Pressure Loss  Turbine Process Branch  Combustor Interface  Condenser

 Few input parameters necessary . Efficiency (polytropic or isentropic) . Outlet pressure (as ratio or fixed) . Leakage (absolute or relative) . Pressure loss (absolute or relative)

 Combined cycles . Interaction of energy conversion cycles with different fluid: CCGT, ST+ORC, …

 Thermodynamic diagrams & QT-diagrams

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 Combined Cycle Gas & Steam

 CO2 Compression with Intercoolers

 Organic Rankine cycles

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T-s Diagram Q-T Diagram

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Comparison: 8 vs. 4 Compression steps

4 Compression steps 8 Compression steps

P=36.2 MW P=31.3 MW

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• Process design • Fluid study Organic Rankine Cycle • Process optimization • Design parameter

Different application areas require individual process design, parameter studies, analyses of fluid variations, …

TDT

 efficient and fast thermodynamic process configuration and calculation of ORC’s  consideration of real gas properties of various fluids  evaluation of state variables  database of fluid property tables

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design of multiple types of processes within definition of boundary one file for study of various parameters or conditions as fluids transferrable heat, upper and lower temperature ranges, etc.

T-s, h-s, p-T, etc. diagrams

definition of component efficiencies, pressure losses, leakage, …

inlet/outlet state variables and component specific results engineering your visions

© by B&B-AGEMA, No. 24 TDT2 – combined cycle configuration for ORC Example: Combined cycle configuration of recuperated air turbine with water cooled intercooler and ORC with isobutane as working fluid

Evaluation of Process chart - required water mass flow for intercooler (e.g. for presentation) - configuration of ORC cycle for waste heat utilization of air turbine - parameter study of air cycle and ORC for highest efficiencies and/or highest power output - Q-T-diagrams for heat exchangers - generate thermodynamic state variables for component design consideration

T-s-diagram for each process

Q-T-diagram of heat exchanger interfaces

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