Specifications, manufacture
and use of MAX exchanger
Heat exchangers are facilities
providing for transferring heat from one heat-carrying
medium flowing on the primary side of the exchanger to
another heat-carrying medium flowing on the secondary side
of the exchanger. One side of the exchanger, i.e. the
piping side, is characterized by substantially higher
hydraulic resistance than the other side – the shell side.
Whilst piping is generally found on the primary side, the
secondary side of the exchanger is normally in the shell.
That largely applies to steam/water systems in which steam
(condensate) are characterized by lower hydraulic
resistance due to lower throughput, and is therefore piped
in tubes.
In respect of heat transfer and hydraulic resistance in a given exchanger, the issue which side of the exchanger is to be the primary or secondary side needs to be considered for each different medium. Thus, e.g., gases have proved to be better led in tubes due to the possibility of increasing the volume of the α-heat-transfer coefficient. On the other hand, what needs to be checked is the gas flow speed – in order to prevent hydraulic resistance from excessive growth. MAX-type exchangers have toughness calculations approved by the Work Safety Inspectorate (IBP) in Ústí nad Labem, and have been tested by the State Test Institute (STI). Moreover, the quality thereof has been practically tested in all major heat production companies. MAX-type exchangers are made of austenitic 17248.4 steel stabilized by titan - with high resistance against intra-granular corrosion.
These work as exchangers of the following types:
Water-water; steam-water; steam-black oil; steam-crude oil; steam-oil; water-oil, natural gas-water. They are moreover used in even further media, particularly in chemical industry.
Exchangers are primarily intended for central heating systems and for hot water production through forced circulation, where the flow rate is high enough to allow for turbulent flow.
They may be used in heavy power industry, in food processing, chemical, pharmaceutical, textile, and construction industry – given its good resilience towards lyes, organic acids, fats, fruit juices, soap solutions, etc.
MAX exchangers are available in through-flow, counter-flow, or of parallel-flow types. Intensive steady heat transfer takes place on inversely wound piping helixes. What the helixes ensure is smooth compensation during piping expansion occurring pending exchanger operation, and the so-called secondary flow, boosting the α-heat-transfer coefficient.
Manufacture of helixes is carried out on a facility that epitomizes an intellectual property of ELTE s.r.o. Helixes are produced accurate to 0,5mm (bending diameter). Pressure testing takes place with every operation, i.e. pressure-tested is each single helix, each tube plate, and ultimately the entire heat exchanger.
In standard version, MAX exchangers are welded, undetachable, all-stainless products, with black steel fittings provided with black coating. If requested by the client, exchangers can be fitted with stainless fittings (to be used in, e.g., food processing industry).
Apart from the base product line, the Company offers the following options:
- a fifth spigot on the exchanger –
providing for hot water circulation;
- thread and flanged spigots, stainless if so requested by client;
- options such as a change of exchanger parameters of groups/classes I, II, III as against the standard, a change of exchanger size as against the standard, change of exchanger material as against the standard – all according to individual customer requirements
Exchangers installed vertically, e.g., typically require a fairly small ground area, yet it is the height thereof that - at times - tends to be a hindrance. In such case the Company will reduce the exchanger height and increase its diameter, adjusting the heating area of the helical curve to match the original parameters. Thus adjusted and made-to-order exchangers are supplied by the Company within a delivery term of up to two (2) weeks. Standard heat exchanger types are on stock, ready for immediate delivery.
MAX exchangers meet all legislation requirements; manufacture thereof is under surveillance of both the Work Safety Inspectorate (WSI) and the Technical Inspection Institute (TII). Each exchanger is accompanied by a passport containing a strength calculation, operating & assembly instructions, plus a warranty certificate. Though an up to five years´ warranty is provided by the Company, the life cycle of its exchangers is much longer.
MAX exchangers are supplied to practically all places in the Czech Republic. Moreover, for part of customers, the Company ensures the assembly of complete heat exchanger plants, or job shop production of conveyable compact stations that are manufactured in its workshops, and - completed - delivered to the customer.
Assembly of MAX exchangers
Assembly of exchangers needs to be carried out in a way that makes the transfer of forces and moments from installation onto sockets impossible. That in practice means that - on the fastened exchanger - fittings are fixed. From those along, the pipes are joined by welding. In order to prevent the occurrence of explosive steam cores in condensate, and particularly in steam-water application, exchangers are expedient to assembly and run in vertical position. However, in certain particular instances, a different position of exchangers is not ruled out. Thus, e.g., in terms of a wear-water installation, the exchanger can be installed in a vertical position. Proper fastening of exchangers upon the construction is usually done using two holders with gaskets and bottom support.
Exchangers are cleaned chemically, and usually through a replacement system. As standard exchanger types are normally on stock, operation is almost uninterrupted.
Cooperation with designerssee questionnaires
Exchangers are designed straight in ELTE company. Also, it is the Company that guarantees the output thereof. Collaboration with designers is pursued as follows: The designer puts on paper the required parameters of the primary and secondary media (i.e. pressures & temperature falls), the required output and pressure loss on both the core and secondary exchanger circuits; thereupon, ELTE s.r.o. will promptly, i.e. usually within one working day, propose - in writing - the size of the exchanger to match the given parameters, and provide the designer with data concerning throughput rates and pressure losses on the core and secondary circuits. In co-operation with the designer, the Company tackles less capital-intensive assignments (of a smaller exchanger and bigger pump type) or operationally less challenging assignments (of a bigger exchanger type, or of parallel-connected exchangers plus minor pump type). Use of exchangers in cooling equipment.
Heat exchangers made by ELTE are used as a highly favourable and efficacious alternative for cooling, heating, evaporation and condensing of cooling agents. As in case of gases, it is usually more apt to lead coolants through helically curved tubes; it namely is in those that - due to centrifugal forces and the subsequent secondary flow and swirls - the heat-transfer coefficient increases, compared to non-curved tubes. In terms of exchanger calculation, the most propitious procedure is to log in the dependency of the heat-transfer coefficient and [kW/(m2*°K)] during the boiling stage or coolant condensation inside the stainless tubes at a w [kg/(m2*sec)] mass rate. That particularly applies for imported blend coolants. Unless the aforementioned dependency is available, what needs to be done is to log in the following thermo-physical parameters of cooling agents, intended for the anticipated range of coolant temperatures and pressures:
1. Density [kg/m3] 2. Specific heat [J/(kg*°K)] 3. Thermal conductivity [W/(m*°K)] 4a. Kinematic viscosity [m2/s] 4b. Dynamic viscosity [Pa*s] 5. Dimensionless Prandtl Number (as an option) 6. Vaporisation heat [J/kg] ; needs to be entered even in case of logging in α-dependency upon w.
Method of tagging MAX exchangers:
MAX x.x - x - x
Diameter of tubes in a bunch
Heating surface
Number of sockets (4 or 5 with a G-socket)
Basic size (2 to 17)
