FAQ

When a company develops a new product and wants to test it to ensure quality and reliability, under the climatic conditions that it will withstand during its life use, transport or storage, it is time to select a climatic chamber to perform the test. What will be the criteria for choosing the chamber? Price, quality, options,…

Many people are tempted to buy equipment based solely on the cheapest price, but there are several points to take into consideration before making the final decision.

Quality, reliability and after-sales service will add value to your purchase. This will ensure a long lifetime of the climatic chamber, which will result in a lower cost of the equipment in the long run.

Nowadays there is a great variety of climatic chambers, so the application for which it is going to be used will determine the type of chamber you need to carry out the most appropriate tests. If you provide as much information as possible to our sales representatives, DYCOMETAL will select the best chamber for your application.

Before purchasing the chamber there are many questions to ask such as:
– Chamber volume
– Temperature ranges
– Humidity ranges
– Temperature gradients
– Standard to be applied
– Water-cooled or air-cooled
– etc…

All these questions will lead you to the chamber that best suits your testing needs.

When we are going to buy a chamber, the first point we usually take into account is the interior volume of the chamber that we are going to need to carry out the test. Each chamber usually has different dimensions in height, width or depth, but which chamber volume is optimal?

The volume of the chamber to be selected will depend on the size of the sample to be introduced and the number of samples to be tested in parallel. Testing one box is not the same as testing several boxes in parallel, which will take up much more space.

First of all, it is important to bear in mind that in order to condition the samples correctly, it is necessary for the air to move around them. Do not block the airflow of the fans at the back of the chamber. Sufficient free space should be left to allow fluid air movement. The standards set a minimum distance between sample and sample, and sample and chamber walls of 50 mm, but if more space is left, the samples will homogenise more quickly.

Also, do not select a chamber that has too much space around a sample, as the energy consumption of the chamber will be higher than what is really necessary. There is virtue in balance.

Therefore, when purchasing a climatic chamber, consider the amount of space you will really need, taking into account the sample(s) you will be testing.

We need to carry out climatic tests on our developed or developing product, but which is the best climatic chamber for us? The answer lies in the product(s) you want to test, as the climatic chamber should be adapted to your needs and not the product to the climatic chamber. Not all standard chambers will be suitable for testing your product. For example, if I am a manufacturer of a pharmaceutical product and I want to perform stability tests, I will not need a climatic chamber with a temperature range from -70ºC to +180ºC, a chamber from +10ºC to +50ºC will be enough. Each market has its own environmental tests.
In order to configure the ideal equipment, the manufacturer of the chamber must have all the information about the product to be tested, to be able to advise you and offer you the climatic chamber that best suits your needs, as well as to be able to advise you about the construction details of the equipment.

Important points to bear in mind:
– Test standards to be used.
The standards establish the environmental criteria to which the parts will be subjected. These standards establish temperature ranges, gradients and times.
– Type of sample to be tested.
The thermal behaviour of each material is different and may affect the performance of the equipment. For example, conditioning 23 kg of aluminium at negative temperatures costs more than conditioning 23 kg of cardboard, their specific heat is different and the heat release during the cycles will be different as well.
– Additional safeguards.
Also the type of specimen to be tested will define whether additional safety features are necessary in case the specimen may release volatile substances during the test or have elements that may explode. If the sample to be tested is very expensive, you will certainly want to protect it.
– Dimensions and number of samples to be tested.
To calculate the optimum chamber volume for your product by optimising the airflow.
– Sample weight.
Important in order to know the total thermal inertia. It is not the same to test 1 kilogram of cardboard than 1 ton of car, the climatic chamber must take into account this point to be reinforced or not.
– Dissipation capacity.
If the sample generates its own heat, the climatic chamber must compensate the energy generated, the mass and therefore must have more cooling capacity to be able to reach the test temperature points established in the standard.

With all these data, DYCOMETAL will be able to define the equipment that best suits your needs and offer you the most suitable climatic chamber for your product.

Once we have selected the most suitable chamber volume, it is time to select the positive and negative temperature ranges to perform the tests. In this case we will focus on the positive temperature ranges that an environmental test chamber can have, i.e. heating.

The climatic chambers have a heating system based on electrical resistors that generate heat, placing a greater number of resistors will increase the heat generated and therefore the upper range of temperatures and higher heating rates.

Normally the standards indicate the positive test temperature, but sometimes it is the sample itself that will mark the maximum temperature range it can withstand. Always select a maximum temperature range in which you will be working.

Depending on the application for which the chamber is to be used:

• +50 ⁰C. A range for environmental stability testing where the product is subjected to the normal ambient temperatures it will encounter throughout its lifetime. It is used for pharmaceutical industry, biotechnology or in some construction materials testing. Its insulation is usually expanded polyurethane.

• +85ºC. They are modular type chambers or intended for industries where it is not necessary large upper temperature limits such as. These chambers will use polyurethane as insulation.

• +150 or 180 ⁰C. Most of the chambers have this temperature range. It is a dedicated range for industrial sector like automotive, electronics, aeronautics, etc. The insulation shall be composed of mineral wool. These ranges should not be exceeded due to the risk of overheating of the cooling oil.

• +200 °C. Range for thermal shock chambers. As both test chambers (hot and cold) are separated, the cooling limit of the cooling oil may be exceeded.

• ≥ +200 °C. This range is used for stoves, ovens or muffles that do not have a cooling system. This allows the upper temperature limit to be raised.

Climatic chambers have the ability to control both positive and negative temperatures. For positive temperature control, the chambers have electrical heating elements for heating, but in the case of negative temperatures there are different cooling options, but most climatic chambers have a mechanical system based on refrigerant gas compressors for cooling.

There are several negative temperature ranges, but it will be the standard to be used and the type of material or sample to be tested that will define the negative range. You have to take into account: the negative temperature range indicated in the standard, the energy dissipation, the amount of mass and the type of material, to be able to make a calculation of the cooling unit and to know if it is the most suitable or not. For example, if you want to lower the temperature of a test to -40°C with a lot of mass and a lot of dissipation, a single compressor chamber will not be sufficient and you will have to select a two-compressor system with a higher negative temperature range.

There are several alternatives for the lower temperature ranges, based on either mechanical cooling or expandable refrigerant.

• Ambient +10ºC. This lower limit is common for chambers without refrigeration. Since the fan generates its own heat, temperatures close to ambient cannot be guaranteed. If a temperature close to ambient is desired, a cooling system will be necessary.

• -25 °C. This is a considerably low range that can be reached by refrigerants commonly used in refrigerators or air conditioners, via a refrigerant gas.

• -40 °C, These types of refrigeration systems are commonly referred to as single-stage systems, as there is only one compressor in the cooling system.

• -70 ºC, Cascade or dual-stage systems. The high stage will be used to cool the low stage, allowing lower temperature limits. The high stage will ensure that there is no overpressure or overheating.

• -86 °C. To achieve this cooling, a triple cascade cooling system is used. This is rare in climatic chambers, however, it is common for ultra-freezers.

• -170 ºC Chambers that reach these limits use liquid nitrogen for cooling. Nitrogen is an inexpensive method of cooling a chamber, however, prolonged use can be costly. It is often used for tests requiring gradients close to 30ºC/min with small volume.

Remember, provide as much information as possible to DYCOMETAL’s technical department, so that they can configure the most suitable equipment for your solution.

Climatic chambers can control either the temperature or the humidity within them. This is a point that is sometimes difficult to understand, because the relative humidity (RH) percentage will depend on the existing temperature. The higher the temperature, the more moisture the air can hold.

Relative humidity is the ratio of the amount of moisture in the air to the amount it can hold. Changing the temperature changes the relative humidity, which makes temperature control very important, since stable temperatures ensure a stable humidity level.

The normal humidity range for test chambers is usually between 10% and 98% RH, ranging from 10°C to 90°C and limited by the dew point. Test chambers use the dew point to establish the relative humidity limit.

The best way to understand this theory is to look at the temperature vs. relative humidity diagram, which indicates the manufacturer’s humidity limits. It is important to work within these limits to prevent damage to the cooling system.

To achieve lower humidity levels, the chamber is usually equipped with an air-drying system to allow the coil to drop below freezing.

Climate testing regulations have well-defined temperature and humidity ranges. Please indicate the regulations you wish to follow so that DYCOMETAL can offer you the most comprehensive equipment in the humidity ranges you need to perform your tests. Since humidity depends on temperature, indicate the temperature points and the humidity at those points you wish to define so that we can properly define the humidification systems.

Among the characteristics of climate or thermal test chambers, there is a variable that indicates the maximum speed that the chamber can reach for both heating and cooling. In order to define this gradient, the test standards to be applied normally indicate the recommended or maximum gradients for performing the tests.

We must not make the mistake of thinking that a higher gradient is better for reducing test times, as these increases can generate greater thermal stresses in the samples and can cause thermal stress within the sample. Many standards establish a maximum gradient to avoid this effect on the samples. Read the test standards carefully in order to select the most appropriate temperature gradient.

Please note that the gradients provided by chamber manufacturers are based on the IEC 60068-3-5 standard, the average temperature rate within the chamber without load and measured between 10% of the positive and negative temperatures of the chamber’s total temperature range. That is, for a climatic chamber from -40°C to +180°C, the temperature gradient according to IEC 60068-3-5 will be between -22°C and +158°C. This information is used to standardise gradient values, but this value is not always useful for selecting the most suitable chamber. The gradient will be reduced depending on the mass to be tested, the type of material, the sample’s heat dissipation capacity, etc. You must provide as much information as possible to ensure that the climatic chamber will meet your needs and those of the sample you wish to test.

Always consult DYCOMETAL’s technical sales department to select the equipment that best suits your needs.

Test chambers remove or add heat from the product to the air, which increases or decreases the temperature in the chamber. The absorbed heat is circulated through the cooling system to the condenser, where it must be expelled. There are two cooling alternatives: air or water.

Standard climatic chambers or those with lower requirements are usually air-cooled, expelling heat directly into the room where they are located, which generates heat within the room itself that must be taken into account.
If the chamber is to be installed in a closed, unconditioned area, it is advisable to contact the manufacturer, as air-cooled chambers do not work reliably if the ambient temperature of the room where they are installed regularly exceeds +28 ºC or +32 ºC.

Another point to consider is dirt. The condenser constantly moves air flows and most chambers have the condenser located near the floor, which allows it to become easily dirty and clogged, increasing the working pressure of the equipment and therefore activating the overpressure safety devices. For greater chamber effectiveness, the condenser must be clean and free of obstructions so that air can circulate properly. Regular cleaning of the condenser will improve the chamber’s performance.

If the chamber is to be located in a dirty environment or where the atmosphere cannot be contaminated by noise, then the solution is to use a remote air cooling system (air condenser), removing the condenser from the chamber and placing it at a distance, usually outside, freeing the room from the heat and noise generated by the system. However, environmental conditions must be taken into account to ensure that the condenser can function properly under the environmental conditions of the country.

Climate chambers need to be cooled in order to perform effective heat exchange and cool the working volume. To perform this exchange, they have a condenser, which can be air-cooled or water-cooled, each with its own advantages and disadvantages. As we have seen above, air condensation is usually the standard for chambers with lower requirements. However, when high temperature gradients are required or the cooling unit’s performance is greater, it is advisable to use a water-cooled condenser, as this will help to reduce the heat and noise generated by the cooling unit. Furthermore, although air condensation is cheaper to install, it is less efficient, with higher operating costs due to its lower thermal efficiency, higher energy consumption and greater noise.

To do this, you need an external cooling unit (chiller) or a water cooling tower that supplies a continuous flow of clean, temperate water (between 5 and 30 ºC) to remove the heat generated during the cooling of the chamber, allowing you to handle more thermal load than air cooling. To avoid water consumption, the best option is a water recirculation unit, a closed circuit that continuously removes water. Another advantage of water-cooled units is that they are not as affected by the external conditions where the equipment is installed and generate less noise.
The disadvantage is that these types of systems require a more complex installation (pipes, pumps, etc.) and an additional investment for the external water cooling system.

Consult our DYCOMETAL technical department for advice on the equipment that best suits your needs.

When we want to purchase a climate chamber that controls temperature and humidity, there is one variable that must be taken into account: the relative humidity control of the test.

Relative humidity is a point that is sometimes difficult to understand and is defined as the amount of water vapor present in the air relative to the maximum possible for given pressure and temperature conditions. In other words, the relative humidity percentage (% r.h.) depends on the current temperature. As the temperature changes, the relative humidity changes; the higher the temperature, the higher the possible relative humidity percentage.

Typically, climate chamber manufacturers provide a temperature versus relative humidity percentage diagram where the chamber can operate. The normal humidity range for test chambers is usually between 10% and 98% r.h., ranging from +10°C to +90°C. It’s important to keep in mind that test chambers use the dew point as a direct indicator of the actual amount of moisture present in the air: a higher dew point means more humid air.

Before purchasing a climatic chamber, analyze the temperature and humidity tests you will need to ensure that your chamber will meet your needs. Check the temperature and humidity diagram provided by the chamber to ensure it can work within these limits. Remember that optional items can be supplied when climatic tests are outside the standard chamber range.

Consult with DYCOMETAL’s technical and commercial department to select the equipment that best suits your needs.