Air-cooled modular chillers, formally known as air-cooled modular water-chilling/heating units, are central air conditioning equipment that uses air as the heat source (or sink) and water as the medium for providing cooling or heating. These units are typically categorized into two types: cooling-only and heat pump. Heat pump units can provide both cooling and heating, offering a dual-purpose solution for summer cooling and winter heating.
The operating principle of air-cooled modular units is based on the vapor-compression refrigeration cycle. In cooling mode, the compressor compresses low-pressure superheated refrigerant vapor from the evaporator into high-temperature, high-pressure superheated vapor. This vapor releases heat to the external environment through the air-cooled condenser, condensing into a saturated or subcooled liquid. After undergoing throttling and pressure reduction through the expansion valve, the refrigerant enters the evaporator, where it absorbs heat from the chilled water and vaporizes. The vapor is then drawn back into the compressor to begin a new cycle. Through this continuous process, the chilled water is consistently cooled and circulated to various rooms to lower the indoor temperature.
In heating mode, a four-way reversing valve alters the flow direction of the refrigerant. The section that previously functioned as a condenser now acts as an evaporator, absorbing heat from the outdoor air. Simultaneously, the original evaporator becomes a condenser, releasing heat into the chilled water to generate hot water for space heating.
Low Outlet Water Temperature in Air-Cooled Modular Units
Low outlet water temperature refers to the chilled water temperature being lower than the expected value in cooling mode, or the hot water temperature failing to reach the set requirement in heating mode. This condition not only compromises the efficiency of the air conditioning system but can also lead to inadequate indoor temperature regulation. Below is a summary of several common causes encountered during maintenance and commissioning for your reference:
1. Insufficient Refrigerant Charge
When the refrigerant charge in the system is insufficient, the refrigerant in the evaporator cannot fully absorb heat, resulting in a drop in evaporation pressure. This not only reduces cooling efficiency but also causes the outlet chilled water temperature to drop further due to the decreased evaporation temperature. Furthermore, the lack of adequate refrigerant to properly cool the compressor causes it to draw in superheated vapor, ultimately leading to compressor overheating.
2. Electronic Expansion Valve Malfunction
The electronic expansion valve is a critical component for precisely controlling the amount of refrigerant entering the evaporator. If this valve malfunctions-such as having an excessively large or small opening, or a slow response rate-it can allow too much or too little refrigerant to flow into the evaporator, disrupting the system's equilibrium. When the liquid supply is inappropriate, the operating conditions of the evaporator change, potentially triggering low-pressure issues that ultimately manifest as abnormal outlet water temperatures.
3. Fouled Heat Exchangers
If the surfaces of the heat exchangers (including both the condenser and evaporator) accumulate deposits of minerals, dust, or other contaminants, a layer of fouling forms. This fouling layer increases thermal resistance and hinders effective heat transfer, thereby reducing heat exchange efficiency. For water-side heat exchangers, scaling is particularly severe, as it decreases the heat transfer coefficient and forces the unit to consume more energy to achieve the same cooling effect.
Suzhou Pharma Machinery Co.,Ltd.
2026/08/14
Gino
