How to combine efficiency and noise levels reduction in cooling towers

We’re to talk about noise levels and efficiency, referred to cooling towers applications. This is a topic we’ve already faced in the past more than once, because evaporative towers while offering high cooling capacities are also a source of noise generated by the moving parts in fans employed to obtain the required air flow.

Noise emission levels became surely a big problem in the case of a Poland gas distribution company that a technological partner of ours, Wentylatory Wentech, grabbed to our attention. The energy sector company had to face back in 2015 the risk of a class action from residentials and recreation centers that along the years were builded in the ponds near the plant.

Tempco ventilatori Wentech torri evaporative

The problem was then to adopt solutions aimed to decrease disturbing noise emissions able at the same time to ensure to same high air flow rates required to maintain the efficiency of the extensive fan cooling towers system installed.

ventilatori torri raffreddamento

The high noise emissions of the evaporative towers have been eliminated thanks to the solution offered by the company Wentylatory Wentech. The supplier verified the gas distributor situation by taking measurements at several dozens points in the plant and the adjacent residential areas. The customer was then offered the quietest 14” blade model fans on the market, which combined the high efficiency rates required with significantly lower noise emissions.

Tempco ventilatori Wentech bassa rumorosità cooling towers

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How to proceed to the correct start-up of a centrifugal pump

We talk again about centrifugal pumps, and in particular about the correct start-up procedure of a pump in order to ensure its proper functioning. This is a very common operation during the commissioning of our thermoregulating units.

The first step in the start-up procedure of a pump is to fill the circuit with the working fluid, water, glicol water or oil, using as reference the minimum level, or just above it, or otherwise the pressure level specified in the technical manual. The next step is to give a small power to the pump, in order to verify the right rotation direction of the pump. This is important to avoid damages to the mechanical seal. If the pump rotates in the wrong direction, one of the three power cables must be switched (we’re clearly talking about three stepper motors).

Next step is to power up the pump, throttling the gate valve installed on the pump’s inlet. While powering up the pump we check the value of the pressure indicated on the pressure gauge on the inlet. The value must be stable. During the start-up of a plant, there will be easily the presence of air bubbles within the circuit, and therefore the measurement will be quite wobbly.

We thus have to open partially the gate valve on the pump’s inlet, stop the pump and proceed to discharge the air from the vents located on the pipes. Then the pump can be re-started. The operation has to be repeated until the pressure level on the inlet gets stable.

Now the pump must be set on it characteristic curve. Read the working pressure specified on the technical manual, and let’s measure the amperes absorbed by the pump. What we have to check is in fact that the pressure drops generated when opening the gate valve on the inlet are such as to maintain the pump in absorption mode. In case the absorption parameters of the engine are exceeded, the motor can indeed get damaged.

These operations are quite easy on plants working with water, but they get a little more complicated when using hydraulic oil or diathermic oil. The higher viscosity of oil requires indeed a longer time to fulfill all the spots of the pipes in the circuit. Very likely there will then be presence of air bubbles in the circuit for a few hours still. In this case, the overall operation must be repeated until the pressure value on the pump’s inlet gets finally stable.

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Renewables and efficiency in the underwater data center Microsoft

An important confirmation of the advantages of data center cooling exploiting the cold and constant temperatures of sea water recently came from Microsoft, with its Natick project, an underwater data center module that was installed in 2018 at a depth of 35 meters on the seafloor in the North Sea. After two years of operations, the data center has just been brought back to the surface and showed a failure rate of servers of approximately one-eight compared to an identical data center structure installed on the ground, therefore with a reliability eight times higher.

underwater-data-centers-microsoft

 

This is another main example of the potential of energy saving and cooling efficiency that can be achieved using water basins, not only for data center cooling but also for example for heat pumps, as showed in the Tempco applications of TCOIL heat exchangers at the Marina di Loano seaport and on the Como lake.

Microsoft datacenter subacqueo

Microsoft’s Natick project was based on the idea of putting the data center in an environment with constant and low temperatures, avoiding fluctuations between day and night that are detrimental for electronics components. And therefore using the cold seawater of the North Sea to cool servers achieving a big energy saving. The data center has also been powered at 100% by wind and solar energy. The structure was then filled only with nitrogen, eliminating oxygen and humidity that cause corrosion on data center equipment. An environment not suitable for human operators, but very much favorable to electronic components.

project_natick_undersea_microsoft_datacenter_1528380408

 

The project achieved very important goals, in terms of higher reliability with lower energy consumption for server cooling, lower risks of damages due to shocks and people moving among the servers. And most of all, an increased sustainability of data centers, since the Microsoft underwater data center was completely powered using renewable energy. A crucial step forward in the direction of future and sustainable data centers, to satisfy the increasing demand related to the spread of cloud and AI applications worldwide.

 

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Centrifugal pumps, types and advantages

We have already talked about centrifugal pumps in the past, and due to the feedback received I want to go a little more in depth on it. Pumps are operating equipments aimed to move fluids, water, oil or other kind of fluids, with a certain flow rate and a certain pressure value at a required height.

First of all, pumps can be divided in two main families, centrifugal pumps, a dynamic kind of pumps, and volumetric pumps.

As the name itself says, volumetric pumps are employed to move huge amounts, big volumes of fluids. Centrifugal pumps use instead a different approach, exploiting the centrifugal force to move fluids.

 

Once again, centrifugal pumps can be divided in two branches, classic centrifugal pumps and peripheral centrifugal pumps. Both of them employ the centrifugal force to move fluids, but peripheral centrifugal pumps are equipped with open type impellers that allow to obtain quite high pressure values with contained power capacity motors.

These are pumps that can be found in applications that don’t need very high flow rates. When the flow rates required increase, it is then mandatory to employ classic centrifugal pumps. But for low flow rates, a peripheral centrifugal pump can be an excellent solution to achieve high pressure values, by using low power capacity motors and therefore quite economical.

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New product, compact 3-in-1 brazed plate exchanger for air dryer

We are to introduce a NEW product that joins the solutions family of Tempco, a brazed plate heat exchanger 3-in-1 which combines an evaporator, a separator and a pre-cooler/heater. The T PLATE B – TCB3000A is the ideal solution for large air dryer applications, under 50 m3/min with up to 10 bar working pressure, for applications in refrigerated air dryer and air compressors.

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.

Tempco TCB3000 A scambiatore 3 in 1

 

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.

 

Scambiatore 3 in 1 essiccatori aria

 

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.

Tempco scambiatore 3 in 1

 

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Coil exchangers for geothermal heat pumps

These are special coil heat exchangers for geothermal heat pumps for brackish water that we’ve supplied a customer a few months ago. These special heat exchangers are aimed for immersion within geothermal wells in a natural park with thermal water in the Naples area.

Geothermal heat pumps, also called ground source heat pumps, are a particular kind of heat pumps employing ground or water as a renewable energy source, instead of air, offering interesting levels of energy saving.

Tempco scambiatori a serpentino

The geoexchange uses the earth as a heat reservoir, thanks to the characteristic that the ground underneath the earth’s surface maintains a nearly constant temperature throughout the whole year, not being affected by daily or seasonal variations of the external temperature. A geothermal heat pump therefore transfers heat from the ground or water, or from thermal water for instance, providing heating during the winter and lowering costs and the use of fossil fuels, while it dissipates heat giving it back to the ground for cooling and conditioning during the summer.

Tempco scambiatori serpentino pompe geotermiche

These particular exchangers employ heat pump water as thermal transfer fluid with the brackish water of the well. We chose the coil type because of the very narrow size of the well, only 220 mm in width, that made it impossible to employ TCOIL dimple jacket plate exchangers. The construction material for this application is tinned copper, in order to ensure corrosion resistance to chlorides.

Tempco scambiatori pompe geotermiche

Tempco scambiatore pompe di calore geotermiche

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How to feed steam in brazed plate heat exchangers

How to handle plate heat exchangers when using them with steam? In case of plate heat exchangers that can be inspected there are no problems, because it’s always possible to maintain and repair them. In case of hammering pressures, steam peaks or condensate that damages the gaskets, it’s indeed possible to open the exchanger, replace the gaskets, closing the exchanger and make a pressure test, and the heat exchanger is ready back to work. A different story with brazed plate exchangers, that cannot be repaired when they get broken.

The main problem with plate heat exchangers using steam happen when there is not a proper condensate discharge, so that condensate remains inside the exchanger. When new steam enters the exchanger in presence of stagnant condensate, the condensate suddenly evaporates and noises such as clicks and cracks can be heard. These are caused by the sudden evaporation of the condensate which leads to very high pressure peaks, that can damage the exchanger irreparably.

 

An efficient condensate discharge must then be installed, ensuring that the discharge pipeline have no counter pressures, in order to achieve a complete draining. A vacuum breaker valve should be installed as well, on the outlet circuit of the steam regulating valve, working in fact as a backwards restraint valve: when the steam flow stops, the vacuum breaker valve opens letting air in, ensuring the complete draining of the exchanger, forcing air and condensate out of it through the condensate discharge.

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Hydraulic passages in plate heat exchangers

An information we are often asked for is the size of hydraulic passages in plate heat exchangers, especially when working with dirty fluids or with particles in suspension.

The actual trend is to decrease the size of passages, in order to obtain a higher turbulence of fluids, even when working with low flow rates, therefore obtaining a more packed transfer network with multiple crossings and angles. The reason of it is to increase the thermal transfer rate, decreasing the required thermal exchange surface for a certain thermal duty, producing smaller and more efficient exchangers, with lower costs and more competitive.

But there are some limits, obviously, because when working with dirty waste water, a small passage can be clogged very quickly. And working in industrial applications, it happens very often, working with not very clean water, some times in open circuit, or even in closed circuits but polluted by the production processes that they serve.

Brazed plate exchangers have passage of approx. 2 mm, which is a very small section. But brazed plate exchangers are conceived ad maintenance-free exchangers, except for chemical washing, the so called cleaning-in-place, which is possible only if the exchanger is not completely clogged.

 

 

Plate heat exchangers that can be inspected have instead a variety of passage sections, based on the thermal design of the exchanger. For example, in our Tempco range of heat exchangers the average section starts from 2,5 mm and goes up to 4 mm, for applications with very dirty fluids or requiring very contained pressure drops. It is also true that pressure drops can be piloted choosing a proper Chevron angle of the plates, and having a larger passage expands the application range of the plate exchangers.

There is also a particular type of plate heat exchangers, called free-flow exchangers, which have no contact points and very large passages. These exchangers are employed in particular production processes, such as paper mill or the food production of fruit juices with big pulp particles in suspension, that could clog a traditional plate heat exchanger very quickly.

Free-flow heat exchangers have very large passages, that can measure 6 mm or even 12 mm. These exchangers don’t exist in all the possible sizes and design plates, and not having contact point they offer a lower resistance to pressure gaps compared to traditional exchangers. In addition, plates have to be constructed with higher thickness, involving higher costs.

How to select the kind of passage in a plate heat exchanger, at last? The selection is clearly based on the kind of application, which defines the type of plates, the size of passages and the depth of the plate corrugation.

 

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Brazed plate exchangers with heat recovery in distillation

The photographs in this post are showing special brazed plate heat exchangers we realized for a chemistry industry in the distillation process.
The exchangers are employed in all of the steps of the process, which include:

– head/bottom recovery on distillation columns
– head condensing on distillation column
– bottom cooling of the distillate
– bottom distillate reboiler
– pre-heating on column feeding

Tempco scambiatori distillazione

 

These are some typical applications in distillation/condensation chemistry plants. In this case the customer chose this solution to have compact sizes and high thermal transfer efficiency, pushing all the phases of the process aiming to limit energy consumption.
Based on thermal duties involved, the brazed exchangers are installed in multiple units in parallel configuration. The brazed exchangers employed are heat exchangers of the TCB3100 and TCB4100 series with flanged dn100 and dn80 connections, which allow to manage processes with very high flow rates.

Tempco saldobrasati distillazione

During the head/bottom recovery on distillation columns we’ve implemented an energy recovery concept, in fact achieving a thermal exchange between the final product and the product entering the distillation column. Is therefore possible to leverage the final product temperatures for pre-heating the incoming product, further increasing the overall process efficiency.

Tempco saldobrasati connessioni

To fulfill the cycle we’ve also supplied two small plate coolers of the TCB H series for high temperatures, aimed to manage a cooling cycle with a thermal gap between the primary and secondary circuit exceeding 160° C.

Tempco connessioni saldobrasati

 

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Cooling towers dealing with cold environments

Evaporative towers are thermal machines employed for water cooling in industrial production processes, for outdoor installation. Very often in Tempco we did applications in geographical areas with extreme climate conditions, with wide thermal excursions and therefore hot summers and very cold winters. We’re speaking of applications such as steel industries, in areas where temperatures go widely down 0° C, even at temperatures of -20° C, -30° C or -40° C. Aimed to serve industrial production processes, cooling towers must always ensure the best performances in every condition. That’s why they are designed and built upon the worst possible conditions, meaning the hot season as they are intended to produce cold water.

In order to ensure the proper functioning during the winter season, the main issue is represented by the temperatures going down to very extreme temperature levels. There are some tricks that are employed in these cases, the first being the employ of anti freeze resistances to maintain a certain minimum temperature of the water inside the tank, preventing it to freeze in case the tower gets arrested.

In fact, while the plant and the tower are working, water continually comes from the production process at temperatures of 30-40° C, and circulating within the tower it’s difficult for it to freeze. But it could occur that the process gets stopped, or the tower must be shut down for maintenance, or even due to vacation periods. The water inside the tank could then freeze.

 

When having big sized tanks, the anti freeze resistances are no more enough. An expedient is to insert some steam pipings, draining exhaust steam inside the tank coming from secondary processes, with an operation called ‘barbotage’. Further tricks are referred to the circulation of the water within the tower: as far as the temperature goes down, fans can be stopped, because the thermal transfer efficiency required decreases. Fans can then be stopped, or in case of EC fans equipped with inverters it’s possible to slow down the speed up to the complete arrest of the fans, as long as the natural ‘chimney effect’ of the tower will be enough to cool the water.

The more the water temperature goes down, the more the ‘chimney effect’ becomes exceeding, also for the thermal duties on the outlet of the tower. The next step is to stop the water from passing through the tower and directly bypassing it to the tank, in order to avoid that the water freezes inside the filling packs, clogging the tower. And also avoiding them to get heavy, with the severe risk they collapse inside the tower.

In case of prolonged cold temperatures, bulkheads can be installed to close the air inlet, limiting the air incoming which could freeze the water passing through or percolating from filling packs.

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