A network of robust pressure sensors, temperature sensors, flow sensors, and liquid level sensors control and optimize the performance of coolant distribution units – essential equipment in data centers.
A typical data center has thousands of servers, and together they generate a significant amount of heat. According to Microsoft, which has more than 300 data center worldwide, 1 MWh of heat energy is produced for every 1 megawatt hour (MWh) of electrical energy consumed. And with the rise of cryptocurrency mining, artificial intelligence, and other high-performance computing (HPC) applications, the number, size, capacity, and heat load of data centers will only continue to increase.
Since excessive heat causes servers to automatically shut down and shortens their lifespan, they need to be kept cool. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) issued thermal guidelines that recommend a temperature range of 18…27°C (~64…81°F) for data processing equipment.
Prevent Overheating with Coolant Distribution Units
There are two main ways to make sure servers do not overheat. Air cooling uses fans and air conditioning to remove hot air and introduce cold air. However, this method alone is often insufficient, which is why new data centers and other HPC facilities use a hybrid approach of air and liquid cooling or rely on liquid cooling alone.
Liquid cooling prevents servers from overheating.
Coolant distribution units (CDUs) are systems that pump a cooling liquid throughout a single server rack or a row of racks. The liquid typically circulates through tubes positioned directly over processing chips or at the rear of a server rack, absorbing the generated heat and carrying it away. Some advanced systems completely immerse the components in a special liquid that is thermally conductive but electrically non-conductive.
In a liquid-to-air CDU, the thermal energy in hot coolant is transferred to ambient air outside the building. In a liquid-to-liquid CDU, the heat exchange is through the building’s HVAC system. Once the liquid is cool again, it is filtered and recirculated.
Regardless of the size or type, CDUs are equipped with a variety of electronic sensors to monitor and control the pressures, temperatures, flow rates, and fluid levels of these smart systems, and to warn operators if leaks or other issues arise.
Pressure Sensors in Coolant Distribution Units
A-10 pressure transmitter
Pressure sensors in the CDUs measure the pressure in the coolant supply and return lines. Based on the difference between the detected pressures, the control system adjusts the pump speed as necessary to maintain optimal pressure and flow for effective cooling.
The machines’ filter conditions can also be monitored by measuring the pressure at their inlets and outlets. In addition, pressure transmitters detect anomalies, such as leaks or pressure spikes, then trigger alarms so that operators can take action to prevent equipment or server damage and ensure system efficiency.
The A-10 is a compact yet high-performance transmitter for pressure measurement and control in cooling systems. Found in industrial applications around the world, this field-proven sensor can tolerate up to 100 million load cycles with almost constant precision. Integration into any type of CDUs is easy, thanks to the A-10’s effortless configurability and universal applicability. It is also highly cost-effective, and the vast majority of orders are shipped within a few days of ordering.
For standard and high-volume applications, the R-1 offers exceptional value and performance. This robust pressure transmitter is expressly designed to monitor and control the condensers, compressors, and boosters in HVAC and refrigeration applications. With stainless steel wetted parts and a hermetically welded thin-film measuring cell, the R-1 is highly resistant to the coolants commonly found in CDUs. OEMs also appreciate the optional private labeling.
Temperature Sensors in Coolant Distribution Units
TR33 mini RTD (left) and TR36 compact RTD
Temperature sensors ensure that the cooling liquid in CDUs remains within the optimal range for efficient heat transfer and to prevent the condensation that can harm electronic components. The resistance thermometers (RTDs) are usually mounted at the intake and outlet points, and the measured data is used to regulate the cooling capacity of the system. Ambient temperature is another crucial parameter that must be monitored in these units.
The TR33 miniature RTD and TR36 compact RTD are ideal for cooling units. These threaded resistance thermometers consist of a thermowell/protection tube with a fixed process connection and is screwed directly into the process. The Pt100/Pt1000 versions offer direct sensor output, while the versions with integrated transmitters have a 4…20 mA output signal. Both offer class A accuracy per IEC 60751. Customer-specific designs are available.
TF35 (left) and TF37 threaded thermometers
The TF35 (with plug connection) and TF37 (with connection lead) are vibration-resistant threaded thermometers with an integrated thermowell for quick and easy insertion directly into the coolant lines, both in the primary (facility) and secondary (server) circuits. The compact sensors’ measuring range extends from −58°F (−50°C) to around 500°F (260°C), and they are available in several measuring elements: Pt100/Pt1000, NTC, KTY81-210; others are available upon request.
For contact temperature monitoring of a CDU’s supply and return lines, the TF-2000 is a reliable and cost-effective solution. The Pt/100/Pt1000 or NTC measuring element is completely encased in thermoplastic elastomer (TPE) for IP68 protection against condensation. It’s easy to mount this cable temperature probe onto pipelines: The probe tip can be inserted into a soldered copper sleeve then fixed with a pipe clamp or cable tie, or affixed to the desired location with the quick-mounting bracket designed for the TF-2000’s square sleeve.
FSD-4 electronic flow switch with optional temperature output
Flow Sensors for Coolant Distribution Units
Flow sensors monitor coolant circulation to ensure that it flows at an optimal rate for efficient heat transfer. If any deviation from the acceptable range is detected, these instruments trigger an adjustment or send out an alarm.
The FSD-4 is expressly designed for the monitoring and control of cooling systems, including the prevention of dry runs in pumps. Thanks to two digital switches, this electronic flow switch can also be programmed for temperature switching. Onsite parameterization is easy with a three-button display, while the IO-Link version allows for not only remote parameterization, but also data collection on variables such as operating hours and maximum/minimum values.
Level Sensors for Coolant Distribution Units
Level sensors monitor and regulate coolant levels within a reservoir, ensuring that they remain within preset limits. If the fluid level falls or rises outside of the ideal range, the level sensor triggers an alarm or makes automatic adjustments via switching operations.
The RLT-1000, based on reed chain technology, provides an amplified current or voltage, or a resistance signal via a 3-wire potentiometer, ensuring accurate and continuous monitoring of the coolant level inside the tank. The RLS-1000 offers up to four switch points that trigger an alarm when specific level thresholds are reached inside the tank. These robust and reliable sensors are made of stainless steel and feature customizable guide tube lengths (150 mm to 1,500 mm), various float options, and adaptable electrical and process connections, making them easy to integrate into various system designs.
OLS-C04 optoelectronic level switch
The OLS-C04 is an optoelectronic level switch designed specifically for the refrigeration industry, featuring a glass prism fused within its steel case. This compact device, mounted on the side of the tank, provides an easy solution for detecting the threshold limit level. It also includes an LED to indicate the switching status.
WIKA continually looks for ways to improve our products’ accuracy, durability, functionality, flexibility, and cost-effectiveness, and that includes solutions for level sensing. We will soon launch a level sensor based on capacitive technology. It will have – among other benefits – the ability to combine multiple functions, including contacts, continuous signaling, and temperature sensing.
WIKA USA, Smart in Sensing for Coolant Distribution Centers
WIKA is a global supplier of robust, accurate, and easily configurable electronic sensors for coolant distribution units and other cooling/refrigeration systems. What’s more, our portfolio of OEM transducers, transmitters, and switches are also cost-effective and available within a short turnaround time of ordering. Contact the knowledgeable product experts at WIKA USA for more information about our measurement solutions for pressure, temperature, flow rate, and liquid level.
Products mentioned in this article
• A-10 pressure transmitter for general industrial applications
• R-1 pressure transmitter for refrigeration and air-conditioning applications
• TR33 miniature resistance thermometer – threaded
• TR36 resistance thermometer – threaded, compact version
• TF35 threaded thermometer with plug connection
• TF37 threaded thermometer with connection lead
• TF-2000 cable temperature probe for heating and refrigeration technology
• FSD-4 electronic flow switch with display for liquid media
• RLT-1000 reed-chain level sensor for industrial applications
• RLS-1000 float switch for industrial applications
• OLS-C04 optoelectronic level switch for refrigeration technology