Schematic diagram of water chiller This describes a closed-loop heat exchange cycle between four core components: compressor, condenser, expansion valve, and evaporator. Refrigerant circulates continuously through these four components, absorbing heat from the cooled water and releasing it to the environment. As a result, the outlet water temperature is maintained at 7°C–12°C (44.6°F–53.6°F), meeting industrial cooling requirements in food processing, seafood processing, pharmaceuticals, and high-capacity air conditioning.
This article analyses each stage of the refrigeration cycle, the technical role of each item of equipment, the principle on the p-h diagram, and the key operating parameters for choosing the right chiller system.
What is a water chiller?
Water Chiller (Water Chiller) is modern industrial heat exchange equipment that lowers water temperature from an entering level of around 12°C–15°C to a standard leaving temperature of 7°C–10°C. This chilled water is then pumped to heat-consuming equipment such as industrial cooling coils, process heat exchangers or machines
To understand its operation and internal construction better, see schematic diagram of water chiller. In an industrial refrigeration system, the chiller is an indirect cooling solution. Instead of letting the refrigerant contact the product directly, water is used as the secondary refrigerant. This is the key advantage of a water chiller over systems using NH3 or Freon directly, because water is a safe, non-toxic medium and extremely flexible to distribute by pipework to many consumption points around a plant.
Today, Tan Long supplies industrial chillers in a wide capacity range from 10 kW to more than 10,000 kW (2.8 RT to 2,840 RT) control cabinet or a PLC monitoring system to keep the system running durably and using electricity efficiently.
How does the water chiller schematic work?
To operate the system effectively, a firm grasp of the schematic diagram of water chiller is essential. The refrigeration cycle in a chiller works on the vapour compression cycle, comprising 4 closed, consecutive thermodynamic processes:
Stage 1: Compression
The system begins when the refrigeration compressor draws in refrigerant vapour at low pressure (around 2–5 bar) and low temperature. The compressor uses electricity to compress the refrigerant to high pressure (condensing pressure, 10–25 bar). This sharply increases the vapour's enthalpy and temperature, producing superheated vapour and supplying the energy the whole thermodynamic cycle needs.
Stage 2: Condensation
The high-pressure superheated vapour is led into the condenser. There the refrigerant rejects heat:
- With water-cooled chillers: The heat is transferred to the water stream through the cooling tower.
- With air-cooled chillers: The heat is rejected directly to the environment by forced-draught fans. The refrigerant changes phase from vapour to liquid at constant pressure. For good performance, the condensing temperature is usually held 5°C–10°C above ambient.
Stage 3: Expansion
High-pressure liquid refrigerant passes through the throttle valve. Because of the sudden change in flow area, the pressure drops sharply from condensing pressure to evaporating pressure. Part of the liquid flashes off instantly, bringing the refrigerant down to the standard evaporating temperature (usually 2°C–5°C), ready to chill the water.
Stage 4: Evaporation
This is the core stage in the schematic diagram of water chiller. The low-pressure liquid-vapour mixture enters the evaporator. There the refrigerant absorbs heat from the chilled water stream, bringing the water down to 7°C–10°C for delivery to the industrial refrigeration. Having fully evaporated, the refrigerant returns to the saturated vapour state and is drawn back by the compressor, starting a new refrigeration cycle.
Construction of the main components in a chiller system
To realise this refrigeration cycle in practice, the components in the schematic diagram of water chiller must be connected consistently and meet demanding technical standards. Below are the 4 core components:
Refrigeration compressor
The compressor is likened to the “heart”, consuming around 70%–85% of the whole system's electricity. At Tan Long, we prefer genuine imported refrigeration compressor to deliver the highest COP.
| Compressor type | Suitable capacity | Key advantages | Limit |
| Screw | 50 kW – 2,000 kW | High reliability, good part-load efficiency | Higher investment cost than scroll |
| Centrifugal | 500 kW – 10,000 kW+ | Extremely high full-load efficiency, little wear | Efficiency falls sharply at loads <50% |
| Scroll | 5 kW – 100 kW | Compact, low vibration, low cost | Not suitable for large capacities |
Practical experience: Tan Long usually recommends screw compressors for seafood cold storage projects, thanks to their ability to hold efficiency steady as the load changes through production shifts.
Condenser
This component rejects heat from the refrigeration cycle to the environment. On the technical drawing of a schematic diagram of water chiller, the condenser typically has a heat rejection ratio of 1.2:1 to 1.3:1.
- Water cooling: Uses water from the cooling tower as the heat-receiving medium. The advantage is a COP reaching 4.0 – 6.0.
- Air cooling: Uses forced-draught fans to reject heat directly into the air through a finned tube coil. This type suits areas short of space or water.
Expansion Valve
This is the device metering refrigerant flow into the evaporator. To optimise the schematic diagram of water chiller, Tan Long usually applies:
- Electronic expansion valve (EEV): modulates flexibly on a signal from the PLC control cabinet, holding suction superheat steady at 5°C–8°C.
- Thermostatic expansion valve (TEV): mechanical modulation, suiting systems with a steady load, at lower cost.
Evaporator
The evaporator is where heat is exchanged directly between the refrigerant and the chilled water. In industrial water chiller systems, the shell-and-tube type is the most favoured. This design provides a standard heat exchange surface area of 0.015–0.025 m²/kW, bringing the water temperature down quickly and to the depth production requires.
The chiller schematic on the p-h diagram
The pressure–enthalpy diagram (p-h diagram, or Mollier diagram) is the technical tool for analysing a chiller cycle. Four points on the p-h diagram correspond to the four stages:
| Point | Refrigerant state | Pressure | Temperature (R-134a example) |
|---|---|---|---|
| 1 | Vapour drawn into the compressor (saturated/slightly superheated vapour) | Low (~3 bar) | ~5°C (41°F) |
| 2 | Vapour leaving the compressor (superheated vapour) | High (~12 bar) | ~70°C–80°C (158°F–176°F) |
| 3 | Liquid leaving the condenser (subcooled liquid) | High (~12 bar) | ~35°C–40°C (95°F–104°F) |
| 4 | After the expansion valve (liquid-vapour mixture) | Low (~3 bar) | ~5°C (41°F) |
The cycle's energy efficiency (COP) equals the enthalpy difference between points 1 and 4, divided by the enthalpy difference between points 2 and 1. With R-134a under the conditions above, the theoretical COP is around 4.5–5.0. In practice, mechanical and thermal losses bring the actual COP of a water-cooled chiller to 4.0–5.5.
Telling water-cooled and air-cooled chillers apart
The difference between these two systems is not only in the condensing equipment. In practice, each type's schematic diagram of water chiller differs clearly in the heat rejection loop, which directly affects installation location, operating cost and the energy efficiency of the whole system.
Water-cooled chiller
This system requires a more complex schematic diagram of water chiller because it needs an additional cooling water circuit.
- The full system comprises: evaporator – refrigeration compressor – shell-and-tube condenser – cooling tower – cooling water pump.
- Characteristic: Although total initial investment is typically 20%–30% higher than air cooling at the same capacity (because of pipework and tower costs), this is the optimal solution for large-capacity industrial cold storage . Electricity costs are considerably lower thanks to the higher COP, optimising the business's long-term ROI.
Air-cooled chiller
Opposite, schematic diagram of water chiller An air-cooled focuses on compactness and high integration.
- The simple system comprises: evaporator – compressor – aluminium-finned condenser coil – forced-draught fans.
- Characteristic: The whole condenser and fan assembly is integrated in one frame, usually installed outdoors or on the roof to use the natural airflow. This system needs no auxiliary water supply, and the cold storage installation or air-cooled chiller process is simpler and easier to maintain. It is the ideal choice for
Key technical parameters when reading a chiller schematic
Technicians and design engineers need a firm grasp of the following parameters to assess a schematic correctly and select equipment:
- Chilled water supply temperature (CHWS): The most common standard is 7°C (44.6°F). Some food processing applications require 2°C–5°C (35.6°F–41°F), which demands a lower evaporating temperature and reduces the COP.
- Chilled water temperature difference (delta-T): The design standard is 5°C (9°F), i.e. 12°C (53.6°F) entering and 7°C (44.6°F) leaving. A larger delta-T (8°C–10°C, for example) reduces pump flow and saves pump energy but requires an evaporator with a larger heat exchange area.
- Energy efficiency (COP and kW/TR): COP = cooling capacity (kW) / electrical power consumed (kW). Equivalent: kW/TR (kilowatts per refrigeration ton, 1 TR = 3.517 kW). High-efficiency chillers achieve a COP > 5.0 (equivalent to < 0.7 kW/TR). Standard chillers on the Vietnamese market typically achieve a COP of 3.5–4.5.
- Condensing temperature: Directly affects compressor discharge pressure and equipment life. A 1°C rise in condensing temperature reduces COP by roughly 2%–3%.
The role of the chiller in the overall industrial refrigeration system
In a large seafood or food processing plant, the chiller does not operate alone but is always a key link combined with other equipment in the overall technical drawing. Understanding the schematic diagram of water chiller helps engineers optimise the distribution of chilled water to consumption points through a dense network of insulated pipework. Specifically, this system fulfils the following key roles:
- Multi-point temperature control: Chilled water from the chiller is delivered to industrial cooling coils in the preparation room to hold 10°C–15°C, or through a plate heat exchanger serving raw material washing and product chilling tanks.
- Optimised operating performance: This integration allows the plant to control the temperature of each area independently, minimising heat loss compared with systems running refrigerant directly through long pipe runs.
- A safe working environment: Because water is the secondary coolant, a chiller system eliminates the risk of toxic refrigerant leaks in areas where many people work.
From real-world experience, Tan Long has successfully delivered many projects combining water chillers with IQF conveyor systems at seafood plants in the Mekong Delta. In the severe climate there, with outdoor temperatures regularly reaching 35°C–38°C, choosing a schematic diagram of water chiller water-cooled unit combined with a chiller cooling tower is the best solution. This keeps the COP steady throughout the production shift and completely prevents the midday rise in condensing pressure — a common weakness of air-cooled chillers — protecting the refrigeration compressor and saving energy.
Operating and maintenance notes for chiller systems
Maintenance schematic diagram of water chiller running stably and at peak efficiency in practice depends entirely on scheduled maintenance. However well a system is designed, its COP will fall if the technical parameters are not tightly controlled. Below are the 4 key control points that Tan Long's technical team always recommends.
- Water quality control: Chilled water and cooling water should be held at an ideal pH of 7.0–8.5 with chloride below 200 ppm. This prevents corrosion and scale forming on the tube surfaces of the evaporator and the chiller cooling tower. In practice, a calcium scale layer just 0.1 mm thick is enough to raise thermal resistance and cut cooling performance.
- Monitoring pressure parameters: In operation, suction and discharge pressures should be logged at least every 4 hours. Suction pressure below design indicates low refrigerant charge or a fault at the expansion valve. Conversely, abnormally high discharge pressure usually stems from a fouled condenser or insufficient cooling water flow, putting pressure on
- Compressor and lubricating oil maintenance: On screw refrigeration compressors, an oil change every 8,000–10,000 hours is mandatory. When the oil content in the refrigerant exceeds 2%, the oil coats the heat exchange surfaces and obstructs heat absorption in the evaporator.
- Data management through automation: Make full use of the PLC control panel to monitor and log operating parameters. Historical data lets technicians analyse trends and spot early signs of falling performance so refrigeration system repairs can be planned in time, avoiding sudden shutdowns that disrupt the production line.
Following these points strictly not only protects the equipment but also keeps the system close to the standard schematic diagram of water chiller , optimising electricity costs and extending the life of the whole installation.
Tan Long's professional chiller system consultancy and design
With more than 20 years of experience in industrial refrigeration, Tan Long approaches every project from a rigorous technical foundation. We supply not only equipment but a complete solution, through a schematic diagram of water chiller drawing personalised to each business's actual needs.
Tan Long's standard consultancy and design process comprises:
- Survey and calculation: measuring the actual heat load and calculating capacity from local climate conditions (temperature, humidity) so the system runs durably.
- Optimising the schematic: selecting the right refrigeration compressor and heat rejection method (air or water) to optimise the COP. Detailed design of the chilled water distribution system and pressure vessel that goes with it.
- Operational automation: Integrating a PLC control panel or SCADA monitoring system so the business can manage operations easily and save electricity.
Today Tan Long supplies water chillers, evaporative condensers and auxiliary equipment directly from its modern manufacturing plant in Tay Ninh (formerly Long An). Mastering the manufacturing technology allows us to minimise delivery times and cold storage installation costs, as well as chiller system costs, for customers in southern and central Vietnam.
To receive a detailed schematic diagram of water chiller drawing and the best design solution for your plant, contact Tan Long's engineering team now:
- Hotline: (+84) 933 357 058
- E-mail: info@tanlongvn.com
- Website: tanlongvn.com
Frequently asked questions about the water chiller schematic
How does a chiller differ from a central air handling unit (AHU)?
The chiller produces chilled water. The AHU (Air Handling Unit) uses that chilled water to cool air. They are two pieces of equipment in the same system and cannot substitute for one another. The chiller schematic describes only the refrigerant cycle that chills water; a full HVAC system diagram additionally includes the AHU, pumps, pipework and control equipment.
Why do industrial chillers commonly use R-134a, R-410A or R-717 (NH3)?
Each refrigerant has different working pressures, latent heat of vaporisation and safety characteristics. R-134a is common in medium-capacity commercial chillers because it is non-flammable and works at moderate pressure. R-717 (ammonia, NH3) has the highest latent heat of vaporisation among common refrigerants (around 1,370 kJ/kg against 198 kJ/kg for R-134a), giving the highest thermodynamic efficiency, but requires stricter safety measures because it is toxic and corrodes copper. Processing plants
When should a chiller be chosen over a direct expansion refrigeration system?
A chiller suits situations where the cooling consumption points are spread across a large area (more than 500 m²), where each area needs precise independent temperature control, or where safety requires the refrigerant to be isolated from the production area. A direct expansion (DX) system suits concentrated cooling loads, short pipe runs under 30 m (98 ft), and requirements below 0°C that an ordinary water chiller cannot meet.
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Is your business in need of a survey, upgrade, or new design for your industrial refrigeration system?
With over 18 years of practical experience leading more than 29 major national projects, Tan Long's team of HVAC engineers is committed to providing accurate thermal load calculations, optimizing the COP efficiency coefficient, switching between natural refrigerants NH3/CO2, and saving 20–30% in operating electricity costs.
Engineer Nguyen Toan Thinh (Technical Director)
With over 18 years of practical experience in directing, consulting, designing, and constructing heavy industrial refrigeration systems, ASRS automated warehouses, and IQF freezing systems across more than 29 major national projects.
