A preventive check before summer is therefore essential to ensure production continuity, consistent performance, and controlled energy consumption.

A system that is not properly checked can encounter a series of interconnected problems during the summer months:

• Reduced cooling capacity, making it impossible to maintain the required process conditions
• Increased energy consumption, as the system operates unpredictably to compensate for inefficiencies
• Alarms and sudden shutdowns, often during peak production periods
• Loss of downstream process efficiency, with consequences for quality and productivity

To safely handle summer loads, a suitable best practice is to plan a systematic system check in advance. The main points to check are the followings:

Cleanliness and condition of heat exchangers. Heat transfer surfaces must be clean and free of deposits or fouling. Even a thin layer of fouling can significantly reduce the overall heat transfer coefficient (U), degrading the unit’s rated performance. The check must include both the process and service sides.

Water circuit and water quality. Pipe scaling, localized corrosion, and deterioration of cooling water quality are among the most common causes of problems during the summer season. It’s important to check the pH, hardness, and concentration of any inhibitors, as well as verify proper circulation within the circuits.

Ventilation and condensation components. In dry coolers and evaporative cooling towers, the condensation section is the first to be affected by high external temperatures. Checking that the fans are working properly, that the fins are clean, and that there are no obstructions to the airflow is essential to avoid compromising the unit’s capacity.

General functional check. The inspection must be completed with a comprehensive functional check: calibration of temperature and pressure controls, condition of control components, alarm management, and verification of the correct operating sequence under peak conditions.

Preventive maintenance conducted before summer allows for the identification and resolution of critical issues while there is still time to do so, avoiding emergency interventions during peak production periods.

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In this context, a highly innovative technology involves the use of CO2 as a refrigerant, replacing traditional refrigerant fluids, also helping to comply with new regulations for refrigeration applications aimed at reducing the environmental impact of the sector. CO2 is in fact a natural resource, available in the atmosphere but also as a waste product in numerous industrial processes. In this regard, rapidly growing are the technologies that ensure the capture, storage and use of CO2, called CCS or CCUS (Carbon Capture and Storage and Carbon Capture Utilization and Storage).

The properties of CO2 in fact make this gas a renewable resource that offers a high rate of heat transfer efficiency, which also increases the safety of applications in the event of leaks within the plants and at the same time guarantees a high potential for emission reduction, with a value of Global Warming Potential equal to 1.

However, in the compression, condensation and evaporation cycles of CO2 it is necessary to work with very high operating pressures, which reach up to 140 bar. A field that opens up new application perspectives for Tempco special brazed exchangers, which thanks to the particular brazing cycle are able to withstand very high working pressures.

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Also in 2023 we have installed a fair number of biogas plants, all equipped complete with chiller, heat exchanger and condensate separator.

All systems are always supplied in full configuration and are delivered ready for installation. Speaking about biogas, of particular interest are therefore the latest applications in the paper mill sector, with the aim of reducing polluting emissions. In fact, paper mills have a high potential for the production of biogas and biomethane, as the production cycle of a paper mill generates large amounts of waste water rich in biodegradable COD (chemical oxygen demand), which lends itself to being treated and valorised for the production of biogas.

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This development therefore allows the use of air-cooled condensers, the classic dry-coolers, adopting a solution that also offers the advantage of eliminating the water consumption involved with evaporative towers and ensuring a much simpler overall maintenance of the plant. In fact, there is no longer the risk of legionella implications due a poor water management or scaling due to the presence of carbonates.

The cooling solutions for the production of expanded polystyrene developed by Tempco therefore use special heat exchangers equipped with stainless steel tubes, a material chosen with the aim of increasing their durability and reliability over time.

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A thermal machine that can be a dry cooler, or a refrigerating group, or a cooling tower. In this case, there are indeed four parameters required for the proper sizing of the machinery: the kind of fluid to be cooled and its flow rate; the inlet temperature, which is the temperature of the fluid as it comes from the process; the outlet temperature, which is the temperature of the fluid required when it goes back to the process; the design ambient air temperature.

Ambient air temperature that in case of a chiller is related to the condensation process, in case of a dry cooler is the temperature of the air that will cool the fluid. And finally, in case of an evaporative tower is the wet-bulb temperature, a key value for the evaporation process.

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CO2 employed as a natural refrigerant gas (R-744) is an excellent alternative to traditional synthetic refrigerants (CFD and HCFC), offering a 0 value of Ozone depletion potential (ODP) and a GWP (Global warming potential) of about 1, far less than that of traditional refrigerants. CO2 has also a very high thermal transfer coeffient, much higher than synthetic refrigerants, is stable and non-toxic, but has to work at very high pressure levels, thus requiring higher standards for the design of refrigeration systems and components. Otherwise, its excellent flow performances allow to significantly reduce the size of compressors and refrigeration equipments, making the overall system more compact.

Furthermore, CO2 is a natural working medium of easy access in the environment, and is also a by-product of many industrial processes and factories, so that refrigeration using CO2 represents an excellent solution for the recovery and recycling of exhaust gas.

Another very important application for high temperature brazed plate exchangers involves fuel cells, using hydrogen which is a optimal candidate for energy of the future as alternative to fossil fuels. Fuel cells are zero emission power generation systems that employ an electrochemical process to obtain electricity and heat from the chemical reaction between hydrogen and oxygen, generating water as by-product. Therefore a totally green and clean power generation solution.

Nowadays there are several and different fuel cells technologies deployed, and brazed plate exchangers are employed in a series of tasks such as pre-heating of air and fuel, cooling of the cell and humidity and vapour management, through energy recovery of the generated heat. All of these applications have in common high temperatures requirements, as well as high corrosion resistance.
In the schemes below, there is a series of examples of brazed plate exchangers applications in different fuel cell related technologies, used in micro-grids, sustainable mobility and for hydrogen production.

Among them there are Solid oxide fuel cells (SOFC) employing exchangers for air pre-heating and heat recovery of thermal energy generated by the oxidation process of hydrogen. In Proton-exchange membrane fuel cells (PEMFC), high temperature brazed plate exchangers are used for heat recovery aimed for water heating. Brazed plate exchangers provide hydrogen pret-heating and exhaust gas heat recovery in trucks using fuel cells, making heavy-transportation sustainable. Finally, brazed plate exchangers are used for ammonia pre-heating in NH3 cracker systems, employed for hydrogen production from NH3 molecules.

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I remember when first attempts started on the market to employ inverters in order to adjust the speed of compressors on refrigerating groups. Inverters are largely employed to regulate speed on electric drives, adjusting the power absorption based on the season conditions. It’s clear indeed that during the summer season, when ambient temperature is higher, a refrigerating group needs the maximum power in order to achieve the refrigeration task required. While during the winter season it requires less amounts of power, due to a series of reasons such as the increased efficiency of the condensation system and the fact that water comes from the production process at lower temperatures.

The study to implement energy saving on refrigerating groups aimed then at adjusting the speed of fans on condensers using EC motors, with electronic control, through inverters. This allows the regulation of the speed of fans based on ambient temperature levels.

The same kind of adjustment was then possible on compressors. Let’s make an example to explain why: when sizing a refrigerating group employed to regulate the temperature of pharmaceutical reactors, the plant must be engineered to provide the maximum capacity required to achieve the cooling task. But there will be also a series of intermediate steps not requiring the maximum design refrigerating capacity, but maybe only at 50% or 30.

In the past it was used to employ multi-compressor plants, with step-compressors, using all of the compressors, or only 2 on 4, or one on 4 for example. The solution allowed to obtain a good energy saving, clearly using a step-approach. Which means, having a four-compressors plant, the possibility to have a 100% capacity, or at 75, 50, 25 or 0%.

A further improvement was to install a collecting tank in order to accumulate refrigerated water to satisfy peaks and hollows on the thermal work diagram. An optimal regulation, that can be furthermore improved.

The improvement consists in the employ of an inverter, which allows to adjust the speeed of the compressor in order to have the correct amount of power at the exact right moment when it’s needed. Which represents the very perfect condition. I remember that the first attempts to install inverters on compressors failed, because these were volumetric piston compressors that when powered by the inverter kept stuck.

The problem has been solved with the adoption of scroll-type compressors, that can be used with inverters. Taking a huge step forward in energy saving applied to refrigerating groups. There are also other possibilities to further enhance energy saving, such as using inverters also on pumps to regulate the pressure, but let’s discuss it in a next video.

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In addition to the measures aimed to replace the kind of refrigerants employed, the constructors of refrigeration equipment are indeed very committed in reducing the amount of gas within the machines. The B series brazed plate exchangers have a patented asymmetric plate design which optimizes the efficiency requiring much less refrigerant, with lower water pressure drop under the same working condition compared to different series.

B series brazed plate exchangers are also compatible with natural refrigerants and alternative refrigerant fluids R290, R32 and R454B with low GWP (Global Warming Potential), pursuing the target to cut CO2 emissions and reduce the environmental impact of the refrigeration sector.

The series offers the following advantages:

• Reduction up to 44% of refrigerant
• Reduction up to 25% of water pressure drop
• Increase up to 19% of water flow rate

A similar approach is also employed in modern air condensed machinery, that more and more are realized using a micro channel design.

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Biogas is a natural fuel, but in order to be employed in cogeneration plants it requires a special dehumidification treatment. This is achieved using systems composed by a chiller and shell and tube exchangers, especially engineered for this kind of application, which cool and dehumidify the biogas using a very cold mix of water and glicol.

In fact, biogas coming from digesters enters the system at temperatures of 35-40° C, and must be cooled at temperatures of approx. 4-5° C, eliminating the maximum possible amount of humidity contained. At this purpose, chillers at very low temperatures are employed, near the freezing point, at +1° C or +2° C.

On the outlet of the exchangers the biogas will then have a relative humidity of 100%, but with an extremely low absolute content of humidity. Installed on the outlet of the exchangers there are also condense separators, big tanks aimed to collect the condenses. Furthermore, on the output of the systems there are also additional filters, providing a further filtration of the biogas, which then is finally ready to enter the engines.

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The exchanger TCB3000A combines a series of patents and is made with stainless steel chevron plates and high purity copper foil. It allows to reach high compactness, with a size reduction by 50% compared to other similar equipments. The solution offers high transfer efficiency and high corrosion resistance.

The patented design of the TCB3000A exchanger integrates an air pre-cooler, a water separator and an evaporator in a unique thermal machine, ensuring low pressure drop and low dew point.

In its working circuit, air compressor compresses hot and moist air to the pre-cooler of the A Series exchanger, where hot and moist air exchanges heat with treated cold air. The chilled moist air then enters the evaporator, lower down its temperature and condensate water out by evaporation. On the next step, the air moves to the separator where condensate water gets separated from air thanks to centrifugal force and gravity. The exclusive no-mesh design of the separator avoid problems of ice and oil-clogging, without the use of filters and ensuring long working life. Finally, the cool and dry air goes back to the pre-heater to be heated to the required working temperature.

The unique 3-in-1 design allows to use directly outlet air, achieving a significant energy saving. The solution is also clogging free and easy to maintain, and is equipped with special patented leakage testing connectors.

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