Zeotropic mixture

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A zeotropicmixture, or non-azeotropic mixture, is a mixture with liquid components that have different boiling points. [1] For example, nitrogen, methane, ethane, propane, and isobutane constitute a zeotropic mixture. [2] Individual substances within the mixture do not evaporate or condense at the same temperature as one substance. [3] In other words, the mixture has a temperature glide, as the phase change occurs in a temperature range of about four to seven degrees Celsius, rather than at a constant temperature. [3] On temperature-composition graphs, this temperature glide can be seen as the temperature difference between the bubble point and dew point. [4] For zeotropic mixtures, the temperatures on the bubble (boiling) curve are between the individual component's boiling temperatures. [5] When a zeotropic mixture is boiled or condensed, the composition of the liquid and the vapor changes according to the mixtures's temperature-composition diagram. [5]

Contents

Zeotropic mixtures have different characteristics in nucleate and convective boiling, as well as in the organic Rankine cycle. Because zeotropic mixtures have different properties than pure fluids or azeotropic mixtures, zeotropic mixtures have many unique applications in industry, namely in distillation, refrigeration, and cleaning processes.

Dew and bubble points

Figure 1: Temperature-Composition diagram of a zeotropic mixture Binary Boiling Point Diagram new.svg
Figure 1: Temperature-Composition diagram of a zeotropic mixture

In mixtures of substances, the bubble point is the saturated liquid temperature, whereas the saturated vapor temperature is called the dew point. Because the bubble and dew lines of a zeotropic mixture's temperature-composition diagram do not intersect, a zeotropic mixture in its liquid phase has a different fraction of a component than the gas phase of the mixture. [4] On a temperature-composition diagram, after a mixture in its liquid phase is heated to the temperature at the bubble (boiling) curve, the fraction of a component in the mixture changes along an isothermal line connecting the dew curve to the boiling curve as the mixture boils. [4] At any given temperature, the composition of the liquid is the composition at the bubble point, whereas the composition of the vapor is the composition at the dew point. [5] Unlike azeotropic mixtures, there is no azeotropic point at any temperature on the diagram where the bubble line and dew lines would intersect. [4] Thus, the composition of the mixture will always change between the bubble and dew point component fractions upon boiling from a liquid to a gas until the mass fraction of a component reaches 1 (i.e. the zeotropic mixture is completely separated into its pure components). As shown in Figure 1, the mole fraction of component 1 decreases from 0.4 to around 0.15 as the liquid mixture boils to the gas phase.

Temperature glides

Different zeotropic mixtures have different temperature glides. For example, zeotropic mixture R152a/R245fa has a higher temperature glide than R21/R245fa. [7] A larger gap between the boiling points creates a larger temperature glide between the boiling curve and dew curve at a given mass fraction. [4] However, with any zeotropic mixture, the temperature glide decreases when the mass fraction of a component approaches 1 or 0 (i.e. when the mixture is almost separated into its pure components) because the boiling and dew curves get closer near these mass fractions. [4]

A larger difference in boiling points between the substances also affects the dew and bubble curves of the graph. [4] A larger difference in boiling points creates a larger shift in mass fractions when the mixture boils at a given temperature. [4]

Zeotropic vs. azeotropic mixtures

Figure 2: Bubble and Dew Curves for Zeotropic Mixtures VLE of a Zeotropic Mixture.png
Figure 2: Bubble and Dew Curves for Zeotropic Mixtures

Azeotropic and zeotropic mixtures have different dew and bubble curves characteristics in a temperature-composition graph. [4] Namely, azeotropic mixtures have dew and bubble curves that intersect, but zeotropic mixtures do not. [4] In other words, zeotropic mixtures have no azeotropic points. [4] An azeotropic mixture that is near its azeotropic point has negligible zeotropic behavior and is near-azeotropic rather than zeotropic. [5]

Zeotropic mixtures differ from azeotropic mixtures in that the vapor and liquid phases of an azeotropic mixture have the same fraction of constituents. [9] This is due to the constant boiling point of the azeotropic mixture. [9]

Boiling

When superheating a substance, nucleate pool boiling and convective flow boiling occur when the temperature of the surface used to heat a liquid is higher than the liquid's boiling point by the wall superheat. [10]

Nucleate pool boiling

The characteristics of pool boiling are different for zeotropic mixtures than that of pure mixtures. [11] For example, the minimum superheating needed to achieve this boiling is greater for zeotropic mixtures than for pure liquids because of the different proportions of individual substances in the liquid versus gas phases of the zeotropic mixture. [11] Zeotropic mixtures and pure liquids also have different critical heat fluxes. [11] In addition, the heat transfer coefficients of zeotropic mixtures are less than the ideal values predicted using the coefficients of pure liquids. [11] This decrease in heat transfer is due to the fact that the heat transfer coefficients of zeotropic mixtures do not increase proportionately with the mass fractions of the mixture's components. [11]

Convective flow boiling

Zeotropic mixtures have different characteristics in convective boiling than pure substances or azeotropic mixtures. [11] Overall, zeotropic mixtures transfer heat more efficiently at the bottom of the fluid, whereas pure and azeotropic substances transfer heat better at the top. [11] During convective flow boiling, the thickness of the liquid film is less at the top of the film than at the bottom because of gravity. [11] In the case of pure liquids and azeotropic mixtures, this decrease in thickness causes a decrease in the resistance to heat transfer. [11] Thus, more heat is transferred and the heat transfer coefficient is higher at the top of the film. [11] The opposite occurs for zeotropic mixtures. [11] The decrease in film thickness near the top causes the component in the mixture with the higher boiling point to decrease in mass fraction. [11] Thus, the resistance to mass transfer increases near the top of the liquid. [11] Less heat is transferred, and the heat transfer coefficient is lower than at the bottom of the liquid film. [11] Because the bottom of the liquid transfers heat better, it requires a lower wall temperature near the bottom than at the top to boil the zeotropic mixture. [11]

Heat transfer coefficient

From low cryogenic to room temperatures, the heat transfer coefficients of zeotropic mixtures are sensitive to the mixture's composition, the diameter of the boiling tube, heat and mass fluxes, and the roughness of the surface. [2] In addition, diluting the zeotropic mixture reduces the heat transfer coefficient. [2] Decreasing the pressure when boiling the mixture only increases the coefficient slightly. [2] Using grooved rather than smooth boiling tubes increases the heat transfer coefficient. [12]

Distillation

Figure 3 Distillation Column. Feed mixture enters from the middle of the column. Low-boiling component collects in the top rectifying section, while high-boiling component collects in the bottom stripping section. Overall mass balance of a distillation column for separation of a binary feed in its components v01.svg
Figure 3 Distillation Column. Feed mixture enters from the middle of the column. Low-boiling component collects in the top rectifying section, while high-boiling component collects in the bottom stripping section.

The ideal case of distillation uses zeotropic mixtures. [14] Zeotropic fluid and gaseous mixtures can be separated by distillation due to the difference in boiling points between the component mixtures. [14] [15] This process involves the use of vertically-arranged distillation columns (see Figure 2). [15]

Distillation columns

When separating zeotropic mixtures with three or greater liquid components, each distillation column removes only the lowest-boiling point component and the highest boiling point component. [15] In other words, each column separates two components purely. [14] If three substances are separated with a single column, the substance with the intermediate boiling point will not be purely separated, [14] and a second column would be needed. [14] To separate mixtures consisting of multiple substances, a sequence of distillation columns must be used. [15] This multi-step distillation process is also called rectification. [15]

In each distillation column, pure components form at the top (rectifying section) and bottom (stripping section) of the column when the starting liquid (called feed composition) is released in the middle of the column. [15] This is shown in Figure 2. At a certain temperature, the component with the lowest boiling point (called distillate or overhead fraction) vaporizes and collects at the top of the column, whereas the component with the highest boiling point (called bottoms or bottom fraction) collects at the bottom of the column. [15] In a zeotropic mixture, where more than one component exists, individual components move relative to each other as vapor flows up and liquid falls down. [15]

The separation of mixtures can be seen in a concentration profile. In a concentration profile, the position of a vapor in the distillation column is plotted against the concentration of the vapor. [15] The component with the highest boiling point has a max concentration at the bottom of the column, where the component with the lowest boiling point has a max concentration at the top of the column. [15] The component with the intermediate boiling point has a max concentration in the middle of the distillation column. [15] Because of how these mixtures separate, mixtures with greater than three substances require more than one distillation column to separate the components. [15]

Distillation configurations

Many configurations can be used to separate mixtures into the same products, though some schemes are more efficient, and different column sequencings are used to achieve different needs. [14] For example, a zeotropic mixture ABC can be first separated into A and BC before separating BC to B and C. [14] On the other hand, mixture ABC can be first separated into AB and C, and AB can lastly be separated into A and B. [14] These two configurations are sharp-split configurations in which the intermediate boiling substance does not contaminate each separation step. [14] On the other hand, the mixture ABC could first be separated into AB and BC, and lastly split into A, B, and C in the same column. [14] This is a non-sharp split configuration in which the substance with the intermediate boiling point is present in different mixtures after a separation step. [14]

Efficiency optimization

When designing distillation processes for separating zeotropic mixtures, the sequencing of distillation columns is vital to saving energy and costs. [16] In addition, other methods can be used to lower the energy or equipment costs required to distill zeotropic mixtures. [16] This includes combining distillation columns, using side columns, combining main columns with side columns, and re-using waste heat for the system. [16] After combining distillation columns, the amount of energy used is only that of one separated column rather than both columns combined. [16] In addition, using side columns saves energy by preventing different columns from carrying out the same separation of mixtures. [16] Combining main and side columns saves equipment costs by reducing the number of heat exchangers in the system. [16] Re-using waste heat requires the amount of heat and temperature levels of the waste to match that of the heat needed. [16] Thus, using waste heat requires changing the pressure inside evaporators and condensers of the distillation system in order to control the temperatures needed. [16] Controlling the temperature levels in a part of a system is possible with Pinch Technology. [17] These energy-saving techniques have a wide application in industrial distillation of zeotropic mixtures: side columns have been used to refine crude oil, and combining main and side columns is increasingly used. [16]

Examples of zeotropic mixtures

Examples of distillation for zeotropic mixtures can be found in industry. Refining crude oil is an example of multi-component distillation in industry that has been used for more than 75 years. [14] Crude oil is separated into five components with main and side columns in a sharp split configuration. [14] In addition, ethylene is separated from methane and ethane for industrial purposes using multi-component distillation. [14]

Separating aromatic substances requires extractive distillation, for example, distilling a zeotropic mixture of benzene, toluene, and p-xylene. [14]

Refrigeration

Zeotropic mixtures that are used in refrigeration are assigned a number in the 400 series to help identify its component and their proportions as a part of nomenclature. Whereas for azeotropic mixtures they are assigned a number in the 500 series. According to ASHRAE, refrigerants names start with 'R' followed by a series of numbers—400 series if it is zeotropic or 500 if it is azeotropic—followed by uppercase letters that denote the composition. [18]

Research has proposed using zeotropic mixtures as substitutes to halogenated refrigerants due to the harmful effects that hydrochlorofluorocarbons (HCFC) and chlorofluorocarbons (CFC) have on the ozone layer and global warming. [3] Researchers have focused on using new mixtures that have the same properties as past refrigerants to phase out harmful halogenated substances, in accordance to the Montreal Protocol and Kyoto Protocol. [3] For example, researchers found that zeotropic mixture R-404A can replace R-12, a CFC, in household refrigerators. [19] However, there are some technical difficulties for using zeotropic mixtures. [3] This includes leakages, as well as the high temperature glide associated with substances of different boiling points, [3] though the temperature glide can be matched to the temperature difference between the two refrigerants when exchanging heat to increase efficiency. [5] Replacing pure refrigerants with mixtures calls for more research on the environmental impact as well as the flammability and safety of refrigerant mixtures. [3]

Organic Rankine cycle

In the Organic Rankine Cycle (ORC), zeotropic mixtures are more thermally efficient than pure fluids. [20] [21] Due to their higher boiling points, zeotropic working fluids have higher net outputs of energy at the low temperatures of the Rankine Cycle than pure substances. [7] [21] Zeotropic working fluids condense across a range of temperatures, allowing external heat exchangers to recover the heat of condensation as a heat source for the Rankine Cycle. [20] The changing temperature of the zeotropic working fluid can be matched to that of the fluid being heated or cooled to save waste heat because the mixture's evaporation process occurs at a temperature glide [20] [21] (see Pinch Analysis).

R21/R245fa and R152a/R245fa are two examples of zeotropic working fluids that can absorb more heat than pure R245fa due to their increased boiling points. [7] The power output increases with the proportion of R152a in R152a/R245fa. [20] R21/R245fa uses less heat and energy than R245fa. [7] Overall, zeotropic mixture R21/R245fa has better thermodynamic properties than pure R245fa and R152a/R245fa as a working fluid in the ORC. [7]

Cleaning processes

Zeotropic mixtures can be used as solvents in cleaning processes in manufacturing. [22] Cleaning processes that use zeotropic mixtures include cosolvent processes and bisolvent processes. [22]

Cosolvent and bisolvent processes

In a cosolvent system, two miscible fluids with different boiling points are mixed to create a zeotropic mixture. [22] [23] The first fluid is a solvating agent that dissolves soil in the cleaning process. [22] [23] This fluid is an organic solvent with a low-boiling point and a flash point greater than the system's operating temperature. [22] [23] After the solvent mixes with the oil, the second fluid, a hydrofluoroether rinsing agent (HFE), rinses off the solvating agent. [22] [23] The solvating agent can be flammable because its mixture with the HFE is nonflammable. [23] In bisolvent cleaning processes, the rinsing agent is separated from the solvating agent. [22] This makes the solvating and rinsing agents more effective because they are not diluted. [22]

Cosolvent systems are used for heavy oils, waxes, greases and fingerprints, [22] [23] and can remove heavier soils than processes that use pure or azeotropic solvents. [23] Cosolvent systems are flexible in that different proportions of substances in the zeotropic mixture can be used to satisfy different cleaning purposes. [23] For example, increasing the proportion of solvating agent to rinsing agent in the mixture increases the solvency, and thus is used for removing heavier soils. [22] [23]

The operating temperature of the system depends on the boiling point of the mixture, [23] which in turn depends on the compositions of these agents in zeotropic mixture. Since zeotropic mixtures have different boiling points, the cleaning and rinse sump have different ratios of cleaning and solvating agents. [23] The lower-boiling point solvating agent is not found in the rinse sump due to the large difference in boiling points between the agents. [23]

Examples of zeotropic solvents

Mixtures containing HFC-43-10mee can replace CFC-113 and perfluorocarbon (PFC) as solvents in cleaning systems because HFC-43-10mee does not harm the ozone layer, unlike CFC-113 and PFC. [23] Various mixtures of HFC-43-10mee are commercially available for a variety of cleaning purposes. [23] Examples of zeotropic solvents in cleaning processes include:

See also

Related Research Articles

<span class="mw-page-title-main">Boiling point</span> Temperature at which a substance changes from liquid into vapor

The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.

<span class="mw-page-title-main">Distillation</span> Method of separating mixtures

Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heating of solid materials to produce gaseous products ; this may involve chemical changes such as destructive distillation or cracking. Distillation may result in essentially complete separation, or it may be a partial separation that increases the concentration of selected components; in either case, the process exploits differences in the relative volatility of the mixture's components. In industrial applications, distillation is a unit operation of practically universal importance, but is a physical separation process, not a chemical reaction. An installation used for distillation, especially of distilled beverages, is a distillery. Distillation includes the following applications:

<span class="mw-page-title-main">Vapor pressure</span> Pressure exerted by a vapor in thermodynamic equilibrium

Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquid's thermodynamic tendency to evaporate. It relates to the balance of particles escaping from the liquid in equilibrium with those in a coexisting vapor phase. A substance with a high vapor pressure at normal temperatures is often referred to as volatile. The pressure exhibited by vapor present above a liquid surface is known as vapor pressure. As the temperature of a liquid increases, the attractive interactions between liquid molecules become less significant in comparison to the entropy of those molecules in the gas phase, increasing the vapor pressure. Thus, liquids with strong intermolecular interactions are likely to have smaller vapor pressures, with the reverse true for weaker interactions.

<span class="mw-page-title-main">Boiling</span> Rapid phase transition from liquid to gas or vapour

Boiling is the rapid phase transition from liquid to gas or vapor; the reverse of boiling is condensation. Boiling occurs when a liquid is heated to its boiling point, so that the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. Boiling and evaporation are the two main forms of liquid vapourization.

<span class="mw-page-title-main">Phase diagram</span> Chart used to show conditions at which physical phases of a substance occur

A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions at which thermodynamically distinct phases occur and coexist at equilibrium.

<span class="mw-page-title-main">Azeotrope</span> Mixture of two or more liquids whose proportions do not change when the mixture is distilled

An azeotrope or a constant heating point mixture is a mixture of two or more components in fluidic states whose proportions cannot be altered or changed by simple distillation. This happens because when an azeotrope is boiled, the vapour has the same proportions of constituents as the unboiled mixture. Azeotropic mixture behavior is important for fluid separation processes.

Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation to fractionate. Generally the component parts have boiling points that differ by less than 25 °C (45 °F) from each other under a pressure of one atmosphere. If the difference in boiling points is greater than 25 °C, a simple distillation is typically used. It is used to refine crude oil.

In thermodynamics, the phase rule is a general principle governing "pVT" systems, whose thermodynamic states are completely described by the variables pressure, volume and temperature, in thermodynamic equilibrium. If F is the number of degrees of freedom, C is the number of components and P is the number of phases, then

<span class="mw-page-title-main">Fractionating column</span> Equipment to separate liquids by distillation

A fractionating column or fractional column is equipment used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on their differences in volatility. Fractionating columns are used in small-scale laboratory distillations as well as large-scale industrial distillations.

<span class="mw-page-title-main">Fractionation</span> Method of separating components of a mixture via phase transition

Fractionation is a separation process in which a certain quantity of a mixture is divided during a phase transition, into a number of smaller quantities (fractions) in which the composition varies according to a gradient. Fractions are collected based on differences in a specific property of the individual components. A common trait in fractionations is the need to find an optimum between the amount of fractions collected and the desired purity in each fraction. Fractionation makes it possible to isolate more than two components in a mixture in a single run. This property sets it apart from other separation techniques.

<span class="mw-page-title-main">Azeotropic distillation</span> Any of a range of techniques used to break an azeotrope in distillation

In chemistry, azeotropic distillation is any of a range of techniques used to break an azeotrope in distillation. In chemical engineering, azeotropic distillation usually refers to the specific technique of adding another component to generate a new, lower-boiling azeotrope that is heterogeneous, such as the example below with the addition of benzene to water and ethanol.

<span class="mw-page-title-main">Continuous distillation</span> Form of distillation

Continuous distillation, a form of distillation, is an ongoing separation in which a mixture is continuously fed into the process and separated fractions are removed continuously as output streams. Distillation is the separation or partial separation of a liquid feed mixture into components or fractions by selective boiling and condensation. The process produces at least two output fractions. These fractions include at least one volatile distillate fraction, which has boiled and been separately captured as a vapor condensed to a liquid, and practically always a bottoms fraction, which is the least volatile residue that has not been separately captured as a condensed vapor.

<span class="mw-page-title-main">Absorption refrigerator</span> Heat-source powered

An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling process. The system uses two coolants, the first of which performs evaporative cooling and is then absorbed into the second coolant; heat is needed to reset the two coolants to their initial states. The principle can also be used to air-condition buildings using the waste heat from a gas turbine or water heater. Using waste heat from a gas turbine makes the turbine very efficient because it first produces electricity, then hot water, and finally, air-conditioning—trigeneration. Absorption refrigerators are commonly used in recreational vehicles (RVs), campers, and caravans because the heat required to power them can be provided by a propane fuel burner, by a low-voltage DC electric heater or by a mains-powered electric heater. Unlike more common vapor-compression refrigeration systems, an absorption refrigerator has no moving parts.

The McCabe–Thiele method is a chemical engineering technique to model the separation of two substances by a distillation column. It uses the fact that the composition at each theoretical tray is completely determined by the mole fraction of one of the two components. This method is based on the assumption of constant molar overflow, which requires that:

In thermodynamics and chemical engineering, the vapor–liquid equilibrium (VLE) describes the distribution of a chemical species between the vapor phase and a liquid phase.

<span class="mw-page-title-main">Condenser (laboratory)</span> Laboratory apparatus used to condense vapors

In chemistry, a condenser is laboratory apparatus used to condense vapors – that is, turn them into liquids – by cooling them down.

<span class="mw-page-title-main">Bubble point</span>

In thermodynamics, the bubble point is the temperature where the first bubble of vapor is formed when heating a liquid consisting of two or more components. Given that vapor will probably have a different composition than the liquid, the bubble point at different compositions are useful data when designing distillation systems.

A separation process is a method that converts a mixture or a solution of chemical substances into two or more distinct product mixtures, a scientific process of separating two or more substance in order to obtain purity. At least one product mixture from the separation is enriched in one or more of the source mixture's constituents. In some cases, a separation may fully divide the mixture into pure constituents. Separations exploit differences in chemical properties or physical properties between the constituents of a mixture.

<span class="mw-page-title-main">Residue curve</span>

A residue curve describes the change in the composition of the liquid phase of a chemical mixture during continuous evaporation at the condition of vapor–liquid equilibrium. Multiple residue curves for a single system are called residue curves map.

VTPR is an estimation method for the calculation of phase equilibria of mixtures of chemical components. The original goal for the development of this method was to enable the estimation of properties of mixtures which contain supercritical components. These class of substances couldn't be predicted with established models like UNIFAC.

References

  1. ↑ Gaspar; Pedro Dinis; da Silva; Pedro Dinho (2015). Handbook of Research on Advances and Applications in Refrigeration Systems and Technologies. IGI Global. p. 244. ISBN   978-1-4666-8398-3 . Retrieved 23 January 2017.
  2. 1 2 3 4 Barraza, Rodrigo; Nellis, Gregory; Klein, Sanford; Reindl, Douglas (2016). "Measured and predicted heat transfer coefficients for boiling zeotropic mixed refrigerants in horizontal tubes". International Journal of Heat and Mass Transfer. 97: 683–695. doi:10.1016/j.ijheatmasstransfer.2016.02.030.
  3. 1 2 3 4 5 6 7 Mohanraj, M.; Muraleedharan, C.; Jayaraj, S. (2011-06-25). "A review on recent developments in new refrigerant mixtures for vapour compression-based refrigeration, air-conditioning and heat pump units". International Journal of Energy Research . 35 (8): 647–669. doi:10.1002/er.1736. ISSN   1099-114X.
  4. 1 2 3 4 5 6 7 8 9 10 11 Herold, Keith; Radermacher, Reinhard; Klein, Sanford (2016-04-07). Absorption Chillers and Heat Pumps, Second Edition. CRC Press. pp. 23–63. doi:10.1201/b19625-4. ISBN   9781498714341.
  5. 1 2 3 4 5 Sweeney, K.A.; Chato, J.C. (May 1996). "The Heat Transfer and Pressure Drop Behavior of a Zeotropic Refrigerant Mixture in a Microfinned Tube" (PDF). Air Conditioning and Refrigeration Center.
  6. ↑ Padleckas, H. (2010-11-10). Wikimedia Commons.
  7. 1 2 3 4 5 Pati, Soobhankar; Drelich, Jaroslaw; Jha, Animesh; Neelameggham, Neale; Prentice, Leon; Wang, Cong (2013). Energy Technology 2013 - Carbon Dioxide Management and other Technologies. The Minerals, Metals & Materials Society. ISBN   978-1-11860-571-4.
  8. ↑ Wilfried, C. (2011-10-18). Wikimedia Commons.
  9. 1 2 Cleveland, J. Cutler; Morris, Christopher (2009-01-01). Dictionary of Energy. Elsevier. p. 34. ISBN   9780080964911. OCLC   890665370 – via Knovel.
  10. ↑ Atkins, Tony; Escudier, Marcel (2013). A Dictionary of Mechanical Engineering. Oxford University Press. doi:10.1093/acref/9780199587438.001.0001. ISBN   9780199587438.
  11. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Radermacher, Reinhard; Hwang, Yunho (2005). Vapor compression heat pumps with refrigerant mixtures. Boca Raton, Florida: Taylor & Francis. pp. 237–244. ISBN   9781420037579.
  12. ↑ Zhang, Xiaoyan; Ji, Changfa; Yuan, Xiuling (2008-10-01). "Prediction method for evaporation heat transfer of non-azeotropic refrigerant mixtures flowing inside internally grooved tubes". Applied Thermal Engineering. 28 (14–15): 1974–1983. doi:10.1016/j.applthermaleng.2007.12.009.
  13. ↑ Petrus, Anthony (2009-11-01). Wikimedia commons.
  14. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Górak, Andrzej; Sorensen, Eva (2014). Distillation: Fundamentals and Principles. Elsevier. pp. 271–300. ISBN   978-0-12-386547-2.
  15. 1 2 3 4 5 6 7 8 9 10 11 12 Stichlmair, Johann (2000). Distillation, 1. Fundamentals. Wiley-VCH Verlag GmbH & Co. KGaA. ISBN   9783527306732.
  16. 1 2 3 4 5 6 7 8 9 Stichlmair, Johann (2000-01-01). "Distillation, 3. Processes". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA. doi:10.1002/14356007.o08_o02. ISBN   9783527306732.
  17. ↑ Asprion, Norbert; Mollner, Stephanie; Poth, Nikolaus; Rumpf, Bernd (2000-01-01). Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA. doi:10.1002/14356007.b03_12.pub2. ISBN   9783527306732.
  18. ↑ Hundy, G. F.; Trott, A. R.; Welch, T. C. (2016). Refrigeration, Air Conditioning, and Heat Pumps. Elsevier. ISBN   978-0-08-100647-4 – via Knovel.
  19. ↑ Dincer, Ibrahim (2000-01-01). "Refrigeration". Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. doi:10.1002/0471238961.1805061819090212.a01.pub2. ISBN   9780471238966.
  20. 1 2 3 4 Wang, J.L.; Zhao, L.; Wang, X.D. (November 2010). "A comparative study of pure and zeotropic mixtures in low-temperature solar Rankine cycle". Applied Energy. 87 (11): 3366–3373. doi:10.1016/j.apenergy.2010.05.016.
  21. 1 2 3 Aghahosseini, S.; Dincer, I. (May 2013). "Comparative performance analysis of low-temperature Organic Rankine Cycle (ORC) using pure and zeotropic working fluids". Applied Thermal Engineering. 54 (1): 35–42. doi:10.1016/j.applthermaleng.2013.01.028.
  22. 1 2 3 4 5 6 7 8 9 10 Owens, JohnG (2011-04-04). Handbook for Critical Cleaning. CRC Press. pp. 115–129. doi:10.1201/b10897-7. ISBN   9781439828274.
  23. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Kanegsberg, Barbara; Burke, John; Bockhorst, Rick; Beeks, Michael; Keller, David; Agopovich, JohnW; Owens, JohnG; Merchant, Abid; Shubkin, RonaldL (2000-12-26). Handbook for Critical Cleaning. CRC Press. doi:10.1201/9781420039825.sec1. ISBN   9780849316555.
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