Thermal and power engineering calculations based
on the use of cloud computing technology
Valery
Ochkov, Vsevolod Znamenskiy
(Moscow Power Engineering Institute)
In this article the technology of cloud computing is described,
based on the use of references to web-functions, purposed for calculation of
different power engineering working substances properties.
Thermal engineering
calculations demand knowledge of thermodynamic and physical properties of
working substances. If such calculations are conducted manually, it is enough to have at hand corresponding tables [1] of
properties of specific working substance. But computer calculations (which are conducted more often nowadays)
demand special program functions, which
return specific values of properties of working substances of power cycles
depending on parameters of the cycle – temperature, pressure, specific enthalpy,
specific entropy, density, etc.
One of the most widespread
and convenient programs on properties of working substances of power
engineering (water and water steam, air and smoke gases) is program
WaterSteamPro [2, 3]. After downloading this program from a site www.wsp.ru and its installation on the computer,
user can utilize corresponding functions on properties of working substances in
his engineering calculations[1].
It will be said about this program in greater details in the end of this article.
But downloading functions from Internet sites or installation from
disks onto user’s computer has one essential lack consisting in the following.
Programs for computers, and
in particular, programs for calculation of thermo physical properties of
individual substances and their mixes are continuously improved. It is
connected with the development of new formulations, that contain directions for
calculating specific properties of concrete substances[2],
or that in existing programs errors and inaccuracies are corrected, and the
area of their application extends, their characteristics (speed, volume of
occupied memory of the computer, etc.) improve. Users of such programs often do
not keep up with these changes and work with out-of-date versions. But this
isn’t the biggest trouble. The trouble comes when user changes his computer and
/ or an operating system on it. That often leads to that old programs cannot be
installed or cease to work on new or updated computers.
In this connection, and also
taking into account the fact that now almost all computers on which engineering,
and in particular thermal calculations, are conducted, have a permanent access to
the Internet, the new technology of work with functions on thermal and physical
properties of working substances of power systems has been offered by the
authors of the given article, based not on downloading,
but on references to the functions,
stored on different sites on the Internet.
The mentioned reference book
on thermo physical properties of working substances of power systems is supplemented
with a site which is placed on a calculation server of the Moscow Power Engineering
Institute (MPEI - www.trie.ru) – see fig. 1.
Along with other open, interactive network reference books useful for thermal
and power engineers [11].
Fig.
1. Moscow Power Engineering Institute
calculation server.
On the reference book’s site
on thermo physical properties of working substances of power systems, separate
areas of the IAPWS-IF97 formulation (see a footnote 2) were selected, on which
properties of water and water steam are calculated:
1. Liquid phase (water)
2. Gaseous phase (steam)
3. Near critical point region
4. Saturation line
5. High temperature region (800
– 2000°Ñ)
If a visitor of the site, shown on fig. 1, for
example needs to specify properties of water steam, he can click on the
reference selected on fig. 1, and pass to the -page of a site, shown on fig. 2.
On this web-page there are new references, that lead to: IAPWS-IF97 formulation
description, "live" calculation on given formulation where the site visitor
can change the initial data (pressure and temperature) and receive not only
result of calculation (parameters of water steam at pressure and temperature
preset values), but also all intermediate values, and the set point on ð – Ò
diagram.
Fig.
2. Site on properties of water steam
From the site, shown on fig. 2, it is also
possible to download corresponding functions for engineering calculator Mathcad
(Mathcad 14, 15 and Mathcad Prime are supported) and to insert them in users
thermal engineering calculations.
Engineering calculator Mathcad is a very
convenient tool for the solution of thermal engineering problems [13]. In the
environment of Mathcad, record of formulas is conducted in the natural notation;
it is possible to use measure units for the control over correctness of
calculations and for more convenient display of their results. In Mathcad it is
very simple to display results of calculations in the form of graphs and diagrams.
These and other useful qualities of Mathcad
package have made it one of the most popular tools of the solution of technical
problems on the computer.
In the environment of Mathcad there is a
convenient tool - reference to other Mathcad-document, which variables and
functions become visible in the
Mathcad-document in which the corresponding reference is done. It is possible
to do such reference on Mathcad-documents (files with expansion *.mcd, *.mcdz, *.xmcd, *.xmcdz, *.mcdx and *.mcdxz) which is stored not only, on a workstation or in a
local computer network, but also on Internet sites. It opens ample
opportunities for realization of a new technology of use of the functions
stored on sites of the Internet without downloading them on the user’s computer.
If, during the solution of thermal engineering problems
in the environment of Mathcad, it is necessary, that the functions returning thermodynamic
properties of working substance, in particular, of water and water steam,
became visible in the user’s document, it is necessary to execute several
simple steps, displayed on fig. 3 and 4.
Fig.
3. Getting URL of the reference to Mathcad file
Fig.
4. Insert of the reference to Mathcad function into
algorithm
On fig. 3 it is shown, how by clicking of the
mouse right button on the reference selected on fig. 2, it is possible through
the description of properties of the reference to receive the URL of the given
function in the Internet and to insert it (reference) into the thermal engineering
calculation (fig. 4). Thus it is possible to make visible all functions
necessary for given calculation – for calculation of the thermal efficiency of
the thermodynamic cycle for example, the beginning of which is shown on fig. 4,
and the end on fig. 5.
Fig.
5. Rankin cycle computation, using references to
functions on properties of water and water steam, stored on the Internet
On fig. 5 also displayed Internet sites where
user can find corresponding Mathcad functions, that are referred to, in the
given algorithm and which are necessary for the calculations on properties of
water and water steam.
The user at his desire can click a mouse on any
reference, shown on fig. 5, download and open the given Mathcad-file containing
corresponding function, to check correctness of the calculation in it. This
document can be kept on a workstation (on the computer) or in a local computer
network of an organization and can be referred to its new place of storage –
not on the Internet (in "clouds"), but on the users local place. It
is done in the event that connection with the Internet is not quite reliable or
limited. But in this case it is better to download at once, on the computer or
into a local network of the organization, all
functions on properties of working substances of power system, by addressing
to the site WaterSteamPro (www.wsp.ru), – see fig. 6.
Fig. 6
One of the web-pages of WaterSteamPro site
After downloading and installing the program
WaterSteamPro on a separate computer or in a local network, functions with
prefixes wsp (water and water steam) and wspg (gases and their mixes) will be
built in the environment of Mathcad, returning thermal and physical properties
of working substances of power systems and many other functions useful in
thermal engineering calculations.
Fig.
7. The example of thermal engineering calculation, using
software package “WaterSteamPro”
So on fig. 7 it is possible to see that after enabling
Mathcad functions of the software package WaterSteamPro it is not necessary to
define areas of IAPWS-IF97 formulation in which calculation is conducted – see
for example functions wspH1PT (area 1 – water) and wspH2PT (area 2 – water
steam), on fig. 5. WaterSteamPro package itself will define this area
automatically – see function wspHPT[3]
on fig. 7 and its description in a dialogue window “insert function”. Besides,
on fig. 7 it is possible to see the work of the function returning specific enthalpy
in dependence not from specified values of pressure and temperature, but from
conditions of expansion of water steam in the turbine – see second dialogue
window on fig. 7. On the basis of program WaterSteamPro the considerable
quantity of thermal engineering calculations is created by MPEI and published
on the MPEI (TU) calculation server.
Technologies of references and downloading,
described in given article, have their advantages and disadvantages. The
compromise (intermediate) technology is an installation on the computer or a
local network of the program WaterSteamPro and its regular updating. If thermal
engineering calculations are conducted on computers with a reliable connection
to the Internet it is possible to apply the technology of the references
described in this article. The technology of references to Internet functions
opens to users a wide set of other useful thermal engineering functions placed
on MPEI (TU) calculation server.
The given work is carried out within the bounds
of the project MPEI (TU) - National Research University: «Information support
of power engineering, power efficiency and power economy (IT EEE) - creation of
the centre on thermal and physical properties of substances and decisions for
power engineering».
Reference:
1.
Ochkov
V.F. A New Reference Book for Power Engineers (9th conference on Power System
Engineering, Thermodynamics & Fluid Flow - ES 2010, June 17 - 18, 2010,
Pilsen, Czech Republic.
2.
Alexandrov
A.A., Ochkov V.F., Orlov K.A. Steam Tables and Diagrams on Mathcad Calculation
Server for Personal Computers, Pocket Computers and Smart Phones // Proceedings
of the 15th International Conference of the Property of Water and Steam, Berlin/Germany,
September 7–11, 2008.
3.
Ochkov
V.F., Alexandrov A.A., Orlov K.A., Ochkov A.V. Thermodynamic Cycles:
Calculations on the Internet // Proceedings of the 7-th Conference «Power
System Engineering, Thermodynamics & Fluid Flow», June 26-27, 2008, Pilsen,
Czech Republic, pp. 165-173