District heating from first to fifth generation 

AEL / Alfa Laval have a wide range of special heat exchangers developed for the HVAC market and we have been working actively with the district energy sector for more than 70 years. 

The investment into the research and development of the Alfa Laval Plate Heat exchangers have played a vital role in district heating systems Globally from the start of generation 1 technology, and the importance of their functionality are increasing for the new generations of district heating, district heating generation 4 and 5.  

Together with consultants, system builders, energy companies and our partners we are driving the transformation of the energy landscape. We are proud to be change agents in this energy transition. Do not hesitate to contact your local Alfa Laval office to hear more about the solutions of tomorrow. 

 

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The AEL Techno System DHW Packaged Plate Heat Exchangers can be programmed to thermally scour the DHW circuit by using our Anti Legionella bypass valves with a two way valve that eliminates legionella and isolates the DHW outlet whilst avoiding any scalding during the Anti Legionella cycle. 

The AEL Techno System Anti Legionella function can be programmed with 64 settings with a visual message on the display in case of probe malfunction or an optional audible alarm can be provided.

The four main factors that influence the growth of legionella are. 

1. TEMPERATURE 
2. WATER FLOW / STAGNATION 
   
3. PARTICULATE MATTER
   
4. NUTRIENT SUPPLY

 

 TEMPERATURE 
1. Legionella exists in low numbers when the temperature is below 20°C
2. Between 20°C and 37°C the growth is rapid and slows down as it reaches 45°C
3. At 50°C 90% of legionella dies off within two hours and at 60°C legionella are killed off within two minutes. 

WATER FLOW STAGNATION
Low or no flow rate of a fluid may cause stagnation which will encourage the growth of legionella.  

PARTICULATE MATTER
Particulate matter may offer protection to the legionella bacteria where they may be killed off in adverse conditions. 

NUTRIENT SUPPLY
Common organisms such as bacteria serve as a nutrient for legionella. 

USING A  PLATE HEAT EXCHANGER TO REDUCE THE RISK OF LEGIONNAIRES DISEASE
Because a Plate Heat Exchanger instantaneously heats up fluids and does not have any storage, they practically eliminate the possibility of any dangerous bacteria growth such as legionella. 

A standard AEL Plate Heat Exchanger can heat up domestic hot water from 10°C to 60°C instantaneously at a continuous flow rate of 5 L/S. 

The AEL Plate Heat Exchanger plates are made from 316 Stainless Steel that has a corrugated profile that creates turbulence as the fluid flows through the unit which also scrubs and also helps to reduce any particulate deposits forming on the plates. 

It is worth noting that using a plate heat exchanger can practically eliminate legionella from the most common sources which have been found to be: 

1. COOLING TOWERS and EVAPOURATOR CONDENSERS. 
2. HOT WATER SYSTEMS 
3. HUMIDIFIERS and AIR WASHERS 

 

A GUIDE ON HOW TO MANAGE THE RISK OF LEGIONELLA
It is important that every installation has a well thought through scheme to prevent or minimise the risks of legionella. 
It is important that a responsible person is employed to manage and implement precautions. 
It is important that records are kept of the precautions taken. 

Contact Us 

• www.aelheatexchangers.co.uk 

• Tel: 0151 336 8837 

• sales@aelheatexchangers.co.uk  

• technical@aelheatexchangers.co.uk

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Using BIM gives Construction Professionals the confidence of knowing that the specified equipment is suitable for the space provided with other components and that the technical information that is automatically provided ensures the equipment will operate as required.

BIM is not CAD, CAD is a drafting tool to create representational lines and arcs whereas BIM provides a rotational digital 3D image of the specified equipment or component that is supported with technical information such as size, height, weight, flow rate, temperature etc.

The use of BIM has been mandatory for public construction projects since 2018 and in all infrastructure projects during July 2019 and the pace of change has meant that most UK Architects and Professional design engineers are all using BIM with the numbers dramatically increasing each year.

In many countries, the use of BIM is mandatory for new building and infrastructure projects. These include Australia, Brazil, Czech Republic, Chile, Denmark, Finland, Japan, Kazakhstan, Latvia, Norway, Singapore, South Korea, the United Kingdom, Ireland and Vietnam.

One very popular feature of BIM is the BIM viewer that allows you to walk through your design. It is not always easy to explain a building plan with clarity to your client with technical drawings even if you completely understand the project, but being able to virtually walk clients through every room in a 3D building and see every fixture and component in place is a great asset when presenting a project.

The post PLATE HEAT EXCHANGERS – WHAT IS BIM (BUILDING INFORMATION MODELLING) appeared first on AEL Heat Exchangers.

A standard FARAL Aluminium radiator can operate at up to 110 oC making it an ideal choice as a heat dump for a solar heating system as it will heat up and cool down very quickly because of the aluminium construction of the radiator.

A properly sized “Heat Dump” in a solar powered water heating system will avoid any damage to the solar panels caused through persistent overheating.

When using a FARAL Aluminium radiator as a heat dump it is normal practice to divert the hot water via a three port valve from the solar panel to the radiator when the cylinder has reached its optimum design temperature.

A “Heat Dump” can be positioned anywhere in or out ( using a diverting valve) of the heating system but please make sure that the KW heat you are trying to remove from the system is not excessive for the area or room it is being positioned as this might make that room very uncomfortable to live in.

It is recommended that any radiator being used as a “Heat Dump” has a full flow of water flowing across it using a lock shield radiator valve on both the flow and return of the radiator rather than a thermostatic valve on the flow that opens and closes according to the room temperature.

Using lock shield radiator valves on the “Heat Dump” or FARAL Aluminium radiator flow and return will stop anybody from adjusting the valve setting from fully open and allow the Solar Powered Central Heating water to circulate unrestricted through the radiator dissipating all the heat required from the solar heating system thus avoiding overheating and damage to the panels and associated controls.

The post WHAT IS A SOLAR HEATING SYSTEM “HEAT DUMP” appeared first on AEL Heat Exchangers.

A heat sink will stop a boiler or Primary heating source such as a boiler from thermally shutting down and can be positioned anywhere in the Central Heating circuit.

It is important that any Appliance or Secondary Circuit being used as a heat sink is at least equal to the KW heat output you are trying to remove from the Primary heating circuit.

If central heating radiators are being used to dissipate heat they must be sized correctly as excessive heat might make that room very uncomfortable to live in.

The most common place to install a heat sink radiator in a small property is in the bathroom because a bathroom radiator can remain on all the time to dry off towels but please check that the output of the bathroom radiator has enough output to be sure it can dissipate the heat required from the PHE quickly enough.

It is recommended that any radiator being used as a heat sink has a full flow of water flowing across it using a lock shield radiator valve on both the flow and return of the radiator rather than a thermostatic valve on the flow that opens and closes according to the room temperature.

Using a lock shield radiator valve on the FARAL radiator flow and return will stop anybody from adjusting the valve setting from fully open and allow the central heating water to circulate unrestricted through the radiator dissipating all the heat required from the heating system thus avoiding overheating and damage to the boiler and associated controls.

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If a pool needs to be emptied for essential maintenance and cracks appear, wall tiles ‘drop off’ or floor tiles ‘lift’ it is usually the contractor who undertook the responsibility to empty and refill the pool that is at fault because they either did not have or follow the correct procedure when carrying out the work.

The cost of restoration works can be considerable so for these reasons AEL has put some essential tips and advice together to help you avoid such costly problems, we recommend that you:

• Plan the whole project around time and temperature.

• Allow sufficient time for every aspect of the operation as cutting corners could be costly.

• Monitor and record every stage of the process.

• Do not exceed the maximum or minimum time intervals or temperature limits provided by structural engineers and suppliers.

If a pool is emptied too quickly, the physical change in weight and temperature may cause structural or tiling failure. Swimming pools, are designed to operate filled with water at a temperature of 27 to 29+°C.

Removing Water from a Swimming Pool Too Quickly

Removing the water from the pool too quickly will suddenly subject the pool to pressures from the surrounding structural construction materials that allowed for weight and from the time of its initial fill. Removing the water too quickly may result in a high to low back-pressure on the tiling as the absorbed water seeks to flow back to the empty shell of the pool.

Heating a Swimming Pool too Quickly

If a pool is heated too quickly, the difference between the temperature of the water and the pool shell can result in thermal shock causing structural and tiling failure to occur. Thermal shock occurs when a thermal gradient causes different parts of the pools structure to expand at different times causing stresses and strains on the structure. When these stresses eventually overcome the strength of the structural material they may well cause cracks to appear.

Filling or Emptying a Swimming Pool Too Quickly

The same structural and tiling failure can be caused by filling or emptying a pool too quickly. Rapid filling or emptying of a heavy mass of water can cause a structure to crack and fail due to the sudden stresses.

The maximum rate of filling or emptying pools should be controlled and monitored in line with the structural engineer’s advice but as a guide the water level should rise or fall approx.700mm every 24 hours with the water input or extraction evenly distributed throughout this period.

Before emptying, allow the pool wall and pool water to cool naturally as close as possible to ambient temperature. It will also lessen the risk if the pool is only emptied at times when there is unlikely to be a frost.

Prior to refilling a pool, try to lower the temperature of the pool shell as close to the temperature of the incoming mains water. The pool water temperature should then be raised at a maximum rate of 0.25° C/hour in line with the structural engineers advice.

Water Quality Standards

Not too long ago it was normal practice to just routinely replace the pool water on an annual basis but since good water quality standards were introduced a water quality procedure is normal practice when maintaining a pool. Thorough back washing at a minimum rate of once a week and fresh water dilution can be combined to provide the recommended level of 30 litres of fresh water per bather, per day. Fresh water dilution limits the building up of the total dissolved solids (TDS) and organic chloramines that cannot be removed by normal filtration and disinfection means the need for an annual complete water replacement programme is no longer required.

Minor Pool Maintenance Without Emptying a Pool

It is possible that minor maintenance on the pool plant can be carried out without emptying a pool by installing isolation valves at the design stage by specialist contractors who are able to carry out underwater remedial work such as the tiling.

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The Delta P is the pressure drop in a heating system which can be defined as the difference in total pressure between two points (e.g A and B) of a fluid carried through the pipework or heating equipment such as a radiator as shown below.

Pressure drop occurs when frictional forces, caused by the resistance to the water flows through the pipe or radiator etc.

The main causes of resistance to the flow of water is the fluid velocity through the pipe or vessel and the fluid viscosity.

Pressure drop increases proportional to the frictional resistance within the heating pipework and heating equipment installed.
A heating system with a large amount of pipe fittings, tube convergence, divergence, turns, surface roughness and other physical properties will affect the overall system pressure drop.

High flow velocities and / or high fluid viscosities result in a larger pressure drop across a section of pipe, pipe fittings or heating equipment.

Low velocity will result in lower or even zero pressure drop.

OVERCOMING THE PRESSURE LOSS BY USING A PUMP
The head or pressure can be overcome by a pump but it must be sized to be at least equal to the total resistance to the flow of water in the whole of the heating circuit.

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Below provides a guide to water flow rates and pressure when sizing a plate heat exchanger.

Low Pressure Installations
A gravity or low Pressure Installation in a standard two storey house with a cold feed water tank in a loft serving a hot water cylinder on the first floor.
The bathroom taps would have approximately 0.2bar pressure.
A shower head would have approximately 0.1bar pressure.
Taps on the ground floor would have approximately 0.4 – 0.5bar pressure.
A kitchen sink cold water tap would be supplied from the incoming mains water supply and would be high pressure at anything above 1bar pressure.

Approximate Guide to Flow Rates for Taps and Showers
Standard basic bath tap ¾” = 0.25 l/s
Standard basic basin taps ½” = 0.166 l/s
Standard basic bath mixer ¾” tap = 1.2 l/s
Monobloc basin mixer with 10-12mm connections = 0.066 l/s to 0.083 l/s
Standard basic ½” kitchen tap = 1.2 l/s
Monobloc sink mixer = 0.13 l/s
A gravity shower on the ground floor with 0.5bar pressure could provide approximately 0.16 l/s to 0.2 l/s so best check with manufacturer.

Mains Fed Systems
Mains fed systems normally operate at 2.5 to 3bar pressure and give good flow rates in excess of .25 l/s to .416 l/s but this can depend on the size of the mains water supply pipe coming into the property..

Water Pressure and Water Flow
Good pressure does not mean you will get good flow and good flow does not mean you will have good pressure. A standard dripping tap can have good pressure but very poor flow rate where as for example a stream can have very good flow rate but very low pressure.

Static and Dynamic Pressures
Static pressure is the pressure when all the taps are turned off and no water flow is occurring. Dynamic pressure is when taps are turned on and the pressure becomes increasingly lower as more taps are opened. As more and more water flows through the system more and more resistance has to be overcome because every pipe length, valve and fitting creates more and more “frictional” resistance to the flow. Lower resistance means less dynamic pressure reduction and greater flow and greater resistance means less flow.

Showers
Gravity showers will only be just adequate so if you want a good shower on a gravity system it will need to be pumped at a pressure of 1bar or above for a single headed shower but if you are using body jets as well then you would need a 2.4 to 3 bar pump. When using a pump in a shower system you must consider the size of your existing hot and cold water tanks.

An average shower time is approximately 8 to 12 minutes.

A twelve minute shower with a flow rate of 0.25 l/s and would use 180 litres of water.

With a split of 60% of hot to 40% of cold water a shower could use about 108 litres of hot water. An average domestic hot water cylinder in a 3 bedroomed house would have an approximate capacity of 117 litres so your 12 minute shower will have used approximately 92% of your hot water capacity.

Note; All of the above is a guide only and actually pressure losses and flow rates should be verified with the manufacturers.

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With over 20 years of experience AEL can confidently provide you with specific technical advice regarding your heating system. We know it can be very confusing when one engineer works with BTU’s and another works with Watts when discussing heat output required for a room so please see our brief explanation below of “What is a BTU” and “What is a Watt”.

WHAT IS A BTU?
A “BTU” (British Thermal Unit) is an older imperial method used to measure the heat energy required to be generated out of a radiator to heat your room.

WHAT IS A Watt?
A “W”(Watt) is the modern International System of Units. It is a standard unit of the heat power required to be generated out of a radiator to heat your room.

How do I convert one BTU to Watts?
BTUs do not convert directly to watts because BTUs measure energy and watts measure power. However, BTUs per hour can be converted to watts; one BTU per hour is approximately 0.293 watts.

How do I convert one Watts to BTU’s?
Similarly, 10,000 BTUs per hour corresponds to 2,930 watts. Conversely, a single watt converts to approximately 3.412 BTUs per hour. Easy to Use Heat Calculator for Your Room If you know the dimensions of the room that you are trying to heat you can access the “Easy to use Heat Calculator” where you will be asked four simple questions and the minimum and maximum output will be provided in both BTU’s and Watts.

How do I choose the right radiator for my room?
Once you know the output required for the room you want to heat up you then need to decide where the radiator will be positioned in the room.

When you have decided on the position of the radiator you will then need to check if there are any height and width restrictions.

When you know the height and length restrictions of your radiator you can begin to look for style of radiator you would prefer to install and see if it will give you the output required to heat your room.

The post WHAT IS A BTU AND JUST WHAT IS A WATT appeared first on AEL Heat Exchangers.

You can save money by avoiding heating parts of your home that are unoccupied or need lower temperatures at certain times of the day, for example bedrooms may not need heating when a lounge does. You can have separate central heating circuits with their own programmer and room thermostat and control those zones by using a series of Motorised Control Valves as shown in Circuit A or a series of Variable Speed Pumps that slow down or speed up depending on the demand from each circuit as shown on Circuit “B”. You can also avoid heating your DHW cylinder when it is not required during a weekday when the family is at work and school.

Circuit A

Circuit B

Main Zonal System Controller
The main zonal system controller will turn the boiler on if required and increase or decrease the hot water supply from the boiler to your central heating or DHW primary circuit (or zone) depending on the demand for heat when you do or do not need it.

The controller will be pre programmed with “on” and “off” time periods as well as temperature limits. A zonal system controller should also let you turn the central heating and domestic hot water on and off at different times and vary the temperature limits with manual overrides.

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