On the Question of the Fields of Application of Steam Drive for Working Machines

I. K. LEBEDEV

In 1952 Prof. L. A. Melent’ev made an attempt to give a general methodology for determining the rational fields of application of steam drive for working machines [1]. As a criterion for comparing energy schemes with steam and electric drive, he introduced a certain quantity Э, which he expresses as

\[ \mathrm{Э}=\frac{W_{np}}{D_{n\cdot np}}, \]

where \(W_{np}\), kWh, is the consumption of electric energy for the electric drive of the working machine;

\(D_{n\,np}\), kg/h, is the steam consumption for the steam drive of the same machine.

Later, the exposition of this methodology was repeated by him in his book [2], with only the change that the quantity Э was denoted by \(\omega\).

It seems to us that the introduction of this criterion is superfluous. As will be shown below, the calculations associated with determining the rational fields of application of steam drive can be simplified if one does not introduce the criterion Э (or \(\omega\)), but uses the generally known efficiency coefficients of thermal power installations. In our discussion we shall be guided by the same three energy schemes that were adopted by Prof. Melent’ev.

1. The energy supply of the drive of working machines is provided from a thermal power plant when there are, at the enterprise or group of enterprises, heat loads whose coverage may be carried out either by using the heat of the exhaust steam of steam drives (Fig. 1, scheme I), or by extracting steam from cogeneration turbines of the thermal power plant in the case of electric drive of working machines (Fig. 1, scheme II).

Scheme I.
Steam drive.

Scheme II.
Electric drive.

Fig. 1

1. The energy supply for the drive of the working machines is provided by a CHP plant, but at the given enterprise there are no heat consumers capable of using the heat of the exhaust steam from the steam drives. In this case, when a steam drive is present, the exhaust steam is used to generate electric power in a low-pressure steam turbine or in the last stages of the CHP turbine (Fig. 2, Scheme I). When an electric drive is present, however, steam expands from the initial to the final parameters in the steam turbine, and the working-machine drive is supplied with electric power from the electric network (Fig. 2, Scheme II).

Scheme I.
Steam drive.

Scheme II.
Electric drive.

Fig. 2

1. The heat supply of the enterprise is provided by the factory boiler house, and the electric supply—from the district electric-power system.

In this case it is possible to use a steam drive with utilization of the exhaust steam for heat-supply needs (Fig. 3, Scheme I), or to use an electric drive and heat supply from the factory industrial boiler house (Fig. 3, Scheme II).

Scheme I.
Steam drive.

Scheme II.
Electric drive.

Fig. 3

For simplicity of the investigation, we shall neglect the presence of steam extractions for regeneration from the CHP turbines, as Prof. Melent’ev also does.

1st case:

Heat supply and electric supply are provided by the factory CHP plant. The exhaust steam is used for heat-supply needs (Fig. 1).

For a given generation of \(W\) kWh of electric power, the hourly steam consumption \(D_1\) kg/hour at the CHP plant supplying steam to the drives of the working machines (Scheme 1) can be represented by the usual energy equation of the turbine.

\[ D_1 = D_{k e} + y_1 D_n \ \text{kg/hour}, \tag{1} \]

where \(D_{k e}\) kg/hour is the steam consumption for the generation of electrical energy in a purely condensing mode;

\(D_n\) kg/hour is the steam consumption for the steam drive of working machines;

\(y_1\) is the coefficient of underproduction of steam extracted for driving the working machines.

As is known,

\[ D_{k e} = \frac{860 W}{(i_0 - i_k)\eta_{oi}\eta_m\eta_2} \ \text{kg/hour}, \tag{2} \]

and the coefficient of underproduction is

\[ y_1 = \frac{i_1 - i_{k1}}{i_0 - i_k}, \tag{3} \]

where \(i_0 - i_k\) kcal/kg is the theoretical heat drop in the CHP turbine;

\(i_1 - i_{k1}\) kcal/kg is the theoretical heat drop from the extraction point to the condenser;

\(\eta_{oi}, \eta_m, \eta_2\) are the internal relative efficiency, the mechanical efficiency, and the generator efficiency.

The steam consumption for the drive of the working machine can be written in the following form:

\[ D_n = \frac{860 W_n}{(i_1 - i_2)\eta_n^n \eta_{oi}^n \eta_m^n \eta_p} \ \text{kg/hour}, \tag{4} \]

where \(W_n\) kW·h is the useful work of the working machine;

\(i_1 - i_2\) kcal/kg is the theoretical heat drop from the extraction point to the exhaust of the working-machine drive;

\(\eta_n^n\) is the efficiency of the heat flow from the turbine to the working machine;

\(\eta_{oi}^n \eta_m^n\) are the internal relative and mechanical efficiencies of the steam drive of the working machine;

\(\eta_p\) is the efficiency of the working machine when operating in the given mode.

Substituting \(D_{k e}\), \(y_1\), and \(D_n\) from equations (2), (3), and (4) into equation (1), we obtain

\[ D_1 = \frac{860 W}{(i_0 - i_k)\eta_{oi}\eta_m\eta_2} + \]

\[ + \frac{860 W_n (i_1 - i_{k1})} {(i_0 - i_k)(i_1 - i_2)\eta_n^n \eta_{oi}^n \eta_m^n \eta_p} \ \text{kg/hour}. \tag{5} \]

The hourly steam consumption \(D_2\) under the same conditions, but with electric drive of the working machines (scheme II), will be

\[ D_2 = \frac{860 (W + W'_n)} {(i_0 - i_k)\eta_{oi}\eta_m\eta_2} + y_2 D_m \ \text{kg/hour}, \tag{6} \]

where \(W'_n\) kW·h is the amount of electrical energy generated by the turbine for use in the drive of the working machine;

\(D_m\) kg/hour is the steam extraction for heat-supply needs;

\(y_2\) is the coefficient of underproduction of steam extracted for heat-supply needs.

The underproduction coefficient in this case will be

\[ y_2=\frac{i_M-i_{k_2}}{i_0-i_k}, \tag{7} \]

where \(i_M-i_{k_2}\) is the theoretical heat drop from the extraction for heat supply to the condenser.

Taking into account that the heat-supply installation (boiler installation) may be located near the steam-turbine installation, as is the case at modern combined heat-and-power plants, the losses of steam from the extraction to the heat-supply installation, as well as the heat losses in this section, may be neglected.

It is not difficult to see that

\[ W_n'=\frac{W_n}{\eta_{mp}\eta_{em}\eta_p}\ \text{kW·h}, \tag{8} \]

where \(\eta_{mp}\) is the efficiency of the transformer and the electric network;
\(\eta_{em}\) is the electromechanical efficiency of the electric drive.

Substituting into equation (6) the value \(W_n'\) from equation (8) and the value \(y_2\) from equation (7), we then obtain

\[ D_2= \frac{860\,W}{(i_0-i_k)\eta_{0i}\eta_m\eta_2} + \frac{860\,W_n}{(i_0-i_k)\eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{em}\eta_p} + D_M\frac{i_M-i_{k_2}}{i_0-i_{k_2}} \ \text{kg/h}. \tag{9} \]

The saving of standard fuel when using an electric drive may be expressed as

\[ \Delta B=b(D_1-D_2)= b\left[ \frac{860\,W_n}{(i_0-i_k)\eta_n^n\eta_{0i}^n\eta_m^n\eta_p} \frac{i_1-i_{k_1}}{i_1-i_2} - \frac{860\,W_n}{(i_0-i_k)\eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{em}\eta_p} - D_M\frac{i_M-i_{k_2}}{i_0-i_k} \right]\ \text{kg/h}, \tag{10} \]

where \(b\) kg/kg is the specific consumption of standard fuel for producing 1 kg of steam in the boiler house of the combined heat-and-power plant.

The theoretical and actual heat drops in the turbine of the combined heat-and-power plant from the initial parameters to the extraction pressure for the steam drive, to the extraction pressure for heat-supply needs, as well as the theoretical and actual heat drops in the steam drive, plotted on the \(is\) diagram, are given in Fig. 4. In addition, this figure shows the theoretical heat drops \((i_1-i_{k_1})\), \((i_M-i_{k_2})\), and \((i_{2g}-i_{k_3})\).

With the same heat demand in both schemes and with full use of the exhaust steam of the steam drives for heat-supply needs, one may write

\[ D_M(i_M-t_M)=D_n(i_{2g}-t_2), \tag{11} \]

and hence

\[ D_M=D_n\frac{i_{2g}-t_2}{i_M-t_M}, \tag{12} \]

where \(i_{2g}\), kcal/kg, is the enthalpy of the steam that has been used in the steam drive;

\(t_M\,^\circ\mathrm{C}\) is the temperature of the condensate from the boilers when they are heated by extraction steam;

\(t_2\,^\circ\mathrm{C}\) is the same when the boilers are heated by exhaust steam from the steam drives.

Fig. 4

Let us assume that in both cases the subcooling of the condensate either is absent or has the same magnitude. In this case, taking into account that \(P_M=P_2\),

\[ t_M=t_2 . \tag{13} \]

Substitute into equation (12) the value of \(D_p\) from equation (4), while at the same time taking equality (13) into account. We then obtain

\[ D_M= \frac{860\,W_n}{(i_1-i_2)\eta_{п}^{п}\eta_{oi}^{п}\eta_{m}^{п}\eta_p}\, \frac{i_{2g}-t_2}{i_M-t_2} \ \text{kg/hour}. \tag{14} \]

Replacing \(D_M\) in equation (10) by its value from equation (14), we shall have

\[ \Delta B= \frac{860\,b\,W_n}{(i_0-i_k)} \left[ \frac{1}{\eta_{п}^{п}\eta_{oi}^{п}\eta_{m}^{п}\eta_p} \left( \frac{i_1-i_{k1}}{i_1-i_2} - \frac{i_{2g}-t_2}{i_M-t_2}\, \frac{i_M-i_{2K}}{i_1-i_2} \right) - \right. \]

\[ \left. - \frac{1}{\eta_{oi}\eta_m\eta_2\eta_{mp}\eta_{\mathrm{em}}\eta_p} \right] \ \text{kg/hour}. \tag{15} \]

From the \(is\) diagram (Fig. 4) it is seen that

\[ i_M=i_1-(i_1-i_2)\eta_{0i} \tag{16} \]

\[ i_{2g}=i_1-(i_1-i_2)\eta_{0i}^{\,n}. \tag{17} \]

Carrying out simple algebraic transformations in the parentheses of the first term of equation (15), which stands inside the square brackets, and taking into account equations (16) and (17), we obtain

\[ \Delta B= \frac{860\,b\,W_n}{i_0-i_k} \left[ \frac{1}{\eta_n^{\,n}\eta_{0i}^{\,n}\eta_m^{\,n}\eta_p\eta_y} - \frac{1}{\eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{\mathrm{e.m}}\eta_p} \right] \ \mathrm{kg/hour}, \tag{18} \]

where

\[ \eta_y= \frac{1}{ \eta_{0i} + \frac{i_{k2}-i_{k1}}{i_1-i_2} - \frac{i_M-i_{k2}}{i_M-t_2} \left(\eta_{0i}-\eta_{0i}^{\,n}\right) }. \tag{19} \]

The specific consumption of standard fuel per kilogram of steam generated in the boiler room can be expressed as

\[ b=\frac{i_0-t_k}{7000\,\eta_{ku}} \ \mathrm{kg/kg}, \tag{20} \]

where \(t_k\ ^\circ\mathrm{C}\) is the temperature of the feed water in the boiler room;
\(\eta_{ku}\) is the efficiency of the boiler installation.

In this case equation (18) can be rewritten in the following form

\[ \Delta B= \frac{860\,W_n}{7000\,\eta_{ku}\eta_t} \left[ \frac{1}{\eta_n^{\,n}\eta_{0i}^{\,n}\eta_m^{\,n}\eta_p\eta_y} - \frac{1}{\eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{\mathrm{e.m}}\eta_p} \right] \ \mathrm{kg/hour}, \tag{21} \]

where \(\eta_t\) is the thermal efficiency of the installation, which is expressed as

\[ \eta_t=\frac{i_0-i_k}{i_0-t_k}. \tag{22} \]

In the case of incomplete use of the exhaust steam for heat-supply needs, we shall express, as did Melent’ev, the fraction of utilization of this steam as

\[ \delta=\frac{D_{\mathrm{isp}}}{D_n}. \tag{23} \]

Then the amount of extraction steam from the intermediate stages of the turbine of the thermal power plant for heat-supply needs when an electric drive is used for the working machines will be

\[ D_M = D_{\mathrm{isp}} \frac{i_{2g}-t_2}{i_M-t_2} = \delta D_n \frac{i_{2g}-t_2}{i_M-t_2} \ \mathrm{kg/hour}. \tag{24} \]

Taking this into account, equation (19) takes the form

\[ \eta_y= \frac{1}{ \delta\eta_{0i} + \frac{(1-\delta)i_1+\delta i_{k2}-i_{k1}}{i_1-i_2} - \frac{i_M-i_{k2}}{i_M-t_2} \left(\eta_{0i}-\eta_{0i}^{\,n}\right)\delta }. \tag{25} \]

To explain the physical meaning of the coefficient \(\eta_y\), we note the following. When steam is extracted for the steam drive, the coeffi-

the percentage of underproduction \(y_1\) as compared with the coefficient \(y_2\), as is evident from a comparison of equations (3) and (7). This factor causes an increase in the steam consumption for the turbines of the TPP. But with electric drive, the generation of electric power by the turbines increases by the amount of energy consumed by the electric drives, which leads to an increase in the steam consumption by the turbines. At the same time, owing to the decrease of \(y_2\) as compared with \(y_1\), the steam consumption by the turbines decreases. The influence of these factors, taken together, is allowed for by the coefficient \(\eta\), which we conventionally call the equalization coefficient.

2nd case:

The power supply is provided from the plant TPP. The exhaust steam of the machine drives is used in a back-pressure turbine or in the last stages of the TPP turbines (Fig. 2) because of the absence of heat consumers.

For a given generation of electric power \(W\) kWh, the steam consumption for the turbine with steam drive of the working machines (scheme 1), with full utilization of the exhaust steam of the drives in the last stages of the turbine, will be expressed as

\[ D_1 = \frac{860 W}{(i_0 - i_k)\eta_{0i}\eta_m\eta_2} + D_n \frac{i_1 - i_{k1}}{i_0 - i_k} - \frac{i_{2g} - i_{k3}}{i_0 - i_k} D_n \ \text{kg/hour}, \tag{26} \]

where \(i_{2g} - i_{k3}\), kcal/kg, is the theoretical heat drop from the exhaust of the steam drive to the condenser.

Taking into account equations (4) and (17), equation (26), after the simplest algebraic transformations, will take the following form:

\[ D_1 = \frac{860 W}{(i_0 - i_k)\eta_{0i}\eta_m\eta_2} + \frac{860 W_n}{(i_0 - i_k)\eta_n^n \eta_{0i}^n \eta_m^n \eta \eta_{\mathrm{yp}}} \ \text{kg/hour}, \tag{27} \]

where

\[ \eta_y = \frac{1}{\eta_{0i}^n + \dfrac{i_{k3} - i_{k1}}{i_1 - i_2}} . \tag{28} \]

The hourly steam consumption with electric drive of the working machines will be

\[ D_2 = \frac{W + W_n'}{(i_0 - i_k)\eta_{0i}\eta_m\eta_2} \ \text{kg/hour}. \tag{29} \]

Taking equation (8) into account, equation (29) can be rewritten in the following form:

\[ D_2 = \frac{860 W}{(i_0 - i_k)\eta_{0i}\eta_m\eta_2} + \frac{860 W_n}{(i_0 - i_k)\eta_{0i}\eta_m\eta_2\eta_{\mathrm{tr}}\eta_{\mathrm{em}}\eta_p} \ \text{kg/hour}, \tag{30} \]

and the saving of reference fuel from the use of electric drive will be

\[ \Delta B = \frac{860 W_n}{7000\,\eta_{\mathrm{ku}}\eta_t} \left[ \frac{1}{\eta_n^n \eta_{0i}^n \eta_m^n \eta_p \eta_y} - \frac{1}{\eta_{0i}\eta_m\eta_2\eta_{\mathrm{tr}}\eta_{\mathrm{em}}\eta_p} \right] \ \text{kg/hour}. \tag{31} \]

With incomplete utilization of the exhaust steam of the steam drives, if we express

\[ \delta = \frac{D_{\mathrm{usp}}}{D_n}, \tag{32} \]

the equation for the equalization coefficient will take the form

\[ \eta_y=\frac{1}{\eta_{0i}^{n}+\dfrac{i_1(1-\delta)+(\delta i_{k3}-i_{k1})}{i_1-i_2}} . \tag{33} \]

3rd case:

The electric power supply is provided from the district electric network, and the heat supply from the factory boiler house (Fig. 3).

The steam consumption by the turbines of the district system for the generation of a specified quantity of electric energy \(W\) kWh with steam drive of the working machines (scheme 1) will be expressed as

\[ D_1^{p}=\frac{860\,W}{(i_0-i_k)\eta_{0i}\eta_m\eta_2}\ \text{kg/hour}. \tag{34} \]

The steam production in the factory boiler house will be

\[ D_1^{k}=\frac{860\,W_n}{(i_1-i_M)\eta_n^{n}\eta_{0i}^{n}\eta_m^{n}\eta_p}\ \text{kg/hour}. \tag{35} \]

The total fuel consumption in the district system and in the factory boiler house will be

\[ B_1=b_pD_1^{p}+b_kD_1^{k} =b_p\frac{860\,W}{(i_0-i_k)\eta_{0i}\eta_m\eta_2}+ \]

\[ +\,b_k\frac{860\,W_n}{(i_1-i_M)\eta_n^{n}\eta_{0i}^{n}\eta_m^{n}\eta_p}\ \text{kg/hour}, \tag{36} \]

where \(b_p\) kg/kg is the specific consumption of standard fuel per kilogram of steam generated in the boiler houses of the district system;

\(b_k\) kg/kg is the same in the factory boiler house.

The specific consumption of standard fuel per 1 kg of steam in the boiler houses of the district system can be expressed by equation (20). As regards the factory boiler house, we shall assume that heat is supplied in the form of hot water heated in boilers. The condensate of the heating steam returns to the boiler house at temperature \(t_M\) and is used as feedwater. In this case the specific fuel consumption in the factory boiler house may be represented as

\[ b_k=\frac{i_1-t_M}{7000\,\eta_{ky}^{n}}\ \text{kg/kg}. \tag{37} \]

Substituting, in place of \(b_p\) and \(b_k\), their values from equations (20) and (37), we shall have

\[ B_1=\frac{860\,W}{7000\,\eta_{ky}\eta_t\eta_{0i}\eta_m\eta_2} +\frac{860\,W_n}{7000\,\eta_{ky}^{n}\eta_t^{n}\eta_{0i}^{n}\eta_m^{n}\eta_p\eta_n^{n}}\ \text{kg/hour}, \tag{38} \]

where

\[ \eta_t^{n}=\frac{i_1-i_M}{i_1-t_M} \]

is the thermal efficiency of the steam-drive cycle of the working machine for the generation of mechanical energy. In this case the installation is considered as a back-pressure one.

In the case of using electric drive of the working machines, the generation of electric energy in the district system must increase by the amount

the release of energy for the drives of working machines. The steam generation in the boiler house of the district system will then be

\[ D_2^p=\frac{860W}{(i_0-i_k)\eta_{0i}\eta_m\eta_2} +\frac{860W_n}{(i_0-i_k)\eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{э.м}\eta_p} \ \text{kg/hour}. \tag{39} \]

and the consumption of equivalent fuel

\[ B_2^p=\frac{860W}{7000\eta_{ky}\eta_t\eta_{0i}\eta_m\eta_2} +\frac{860W_n}{7000\eta_{ky}\eta_t\eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{э.м}\eta_p} \ \text{kg/hour}. \tag{40} \]

In the case of using electric drive for the working machines, the factory boiler house will generate steam only for the needs of heat supply; for this purpose we shall take the required amount of heat to be equal to the amount of heat released with the exhaust steam of the steam drives when it is fully utilized. In this case

\[ D_{om}(i_{om}-t_{om})=D_1^k(i_m-t_m), \tag{41} \]

where \(D_{om}\) kg/hour is the amount of steam generated by the factory boiler house for the needs of heat supply;
\(i_{om}, t_{om}\) kcal/kg are the enthalpy of the steam generated by the factory boiler house and of the condensate of this steam returned from the boilers.

From equation (41)

\[ D_{om}=D_1^k\frac{i_m-t_m}{i_{om}-t_{om}}\ \text{kg/hour}. \tag{42} \]

Substituting into the last equation the value of \(D_1^k\) from equation (35), we shall have

\[ D_{om}=\frac{860W_n}{(i_1-i_m)\eta_n^n\eta_{0i}^n\eta_m^n\eta_p} \frac{i_m-t_m}{i_{om}-t_{om}}\ \text{kg/hour}. \tag{43} \]

If the specific consumption of equivalent fuel in the factory boiler house is taken as

\[ b_k=\frac{i_{om}-t_{om}}{7000\eta_{ky}^n}\ \text{kg/kg}, \tag{44} \]

then the consumption of equivalent fuel in the factory boiler house will be

\[ B_2^k=\frac{860W_n}{7000\eta_{ky}^n\eta_n^n\eta_{0i}^n\eta_m^n\eta_p} \frac{i_m-t_m}{i_1-i_m}\ \text{kg/hour}. \tag{45} \]

Add to the numerator of the last multiplier in equation (45) and subtract from it the same quantity \(i_1\). After this, simple transformations give

\[ B_2^k= \frac{860W_n}{7000\eta_{ky}^n\eta_n^n\eta_t^n\eta_{0i}^n\eta_m^n\eta_p} - \frac{860W_n}{7000\eta_{ky}^n\eta_n^n\eta_{0i}^n\eta_m^n\eta_p} \ \text{kg/hour}. \tag{46} \]

The total consumption of equivalent fuel in the district system and the factory boiler house is obtained as

\[ \begin{aligned} B_2=B_2^p+B_2^k &=\frac{860W}{7000\eta_{ky}\eta_t\eta_{0i}\eta_m\eta_2} +\frac{860W_n}{7000\eta_{ky}\eta_t\eta_{0i}\eta_n\eta_{mp}\eta_{э.м}\eta_p} \\ &\quad+\frac{860W_n}{7000\eta_{ky}^n\eta_n^n\eta_t^n\eta_{0i}^n\eta_m^n\eta_p} -\frac{860W_n}{7000\eta_{ky}^n\eta_n^n\eta_{0i}^n\eta_m^n\eta_p} \ \text{kg/hour}. \end{aligned} \tag{47} \]

The saving of reference fuel when an electric drive is used will be

\[ \Delta B = B_1 - B_2 = \frac{860 W_n}{7000} \left[ \frac{1}{\eta_{ky}^{n}\eta_{n}^{n}\eta_{0i}^{n}\eta_{m}^{n}\eta_p} - \frac{1}{\eta_{ky}\eta_t\eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{\mathrm{em}}\eta_p} \right] \ \text{kg/hour}. \tag{48} \]

With incomplete utilization of the exhaust steam of steam drives for heat-supply needs

\[ D_{ot}=\delta D_i^{*}\frac{i_M-t_M}{i_{ot}-t_{ot}}\ \text{kg/hour}, \tag{49} \]

and

\[ \Delta B = \frac{860 W_n}{7000} \left[ \frac{1}{\eta_{ky}^{n}\eta_n^{n}\eta_t^{n}\eta_{0i}^{n}\eta_m^{n}\eta_p\eta_y} - \frac{1}{\eta_{ky}\eta_t\eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{\mathrm{em}}\eta_p} \right] \ \text{kg/hour}, \tag{50} \]

where

\[ \eta_y=\frac{1}{(1-\delta)+\delta\eta_t^{n}}. \tag{51} \]

CONCLUSION

From the analysis presented it is clear that, in order to determine the advantage of an electric or steam drive in one or another power-engineering scheme, there is no need to introduce any new concepts such as those introduced by Prof. Melent’ev, which, incidentally, do not facilitate but rather complicate understanding of the essence of the question under consideration; one may instead use the widely known efficiencies of heat-power installations.

The electric drive, as is evident from equations (21), (31), and (50), will be more advantageous than the steam drive if:

for the power-engineering scheme according to Figs. 1 and 2,

\[ \eta_n^{n}\eta_{0i}^{n}\eta_m^{n}\eta_p\eta_y < \eta_{0i}\eta_m\eta_2\eta_{mp}\eta_{\mathrm{em}}\eta_p, \tag{52} \]

for the power-engineering scheme according to Fig. 3,

\[ \eta_{ky}^{n}\eta_n^{n}\eta_t^{n}\eta_{0i}^{n}\eta_m^{n}\eta_p\eta_y < \eta_{ky}\eta_t\eta_{0i}\eta_2\eta_{mp}\eta_{\mathrm{em}}\eta_p. \tag{53} \]

LITERATURE

1. Melent’ev L. A.—On the fields of application of steam drive for working machines, For Fuel Economy, No. 2, 1952.

2. Melent’ev L. A.—Basic Questions of Industrial Thermal Power Engineering. GEI, Moscow—Leningrad, 1954.