Cooling and Heating Source System

Introduction to Cooling and Heating Source Systems

The cooling and heating source monitoring system is a monitoring system capable of real-time tracking of the operational status of air conditioning, HVAC, refrigeration, and other systems, while also enabling automated maintenance, energy measurement, and emergency response. This system requires real-time monitoring of operational parameters and feeds the monitored data back to the system controller. This article will introduce the monitoring principles and key implementation techniques of the system.

1. Chiller Units: Water-cooled heat pump units operate on the same principle as chiller units under cooling conditions, while air-cooled heat pump units have simpler controls (no cooling water circulation system; the outdoor unit of the air-cooled heat pump assumes the function of the cooling water circulation in water-cooled heat pump units, and the outdoor unit is self-controlled by the heat pump unit's built-in controller).

2. Chilled Water Circulation: The chilled water circulation in a building's air conditioning cooling source system is shown in the left half of the diagram. It sends high-temperature chilled water, circulated back from air handling equipment on each floor, to the chiller unit for cooling, and then supplies it back to the air handling equipment.

3. Cooling Water Circulation: The cooling water circulation in a building's air conditioning cooling source system is primarily responsible for releasing the heat absorbed by the chiller unit from the chilled water circulation to the outdoors.

4. Inter-unit Coordination and Group Control of Chiller Units: The chiller unit is the core equipment of the building's air conditioning cooling source system. Both chilled water circulation and cooling water circulation are controlled based on the operational status of the chiller unit.

5. Variable Frequency Control Scheme for Secondary Pumps in Chilled Water Circuits: As mentioned earlier, when constant-flow pumps are used in chilled water circuits, a bypass circuit should be installed on the chilled water supply and return mains to balance the pressure in the water pipes by controlling the opening of the bypass valve. This addresses the conflict between variable flow on the load side and constant flow on the chiller side, preventing pump impact on the pipeline and the pump itself under low-load conditions (when load-side coil water valves are simultaneously closed).

6. Ice Storage System: The basic concept of ice storage is to produce and store ice during off-peak electricity hours at night and melt the ice to provide cooling during peak hours in the daytime.

Chiller Unit Control:

Start/stop control and status monitoring of chiller units.

Fault alarm monitoring for chiller units.

Manual/automatic control status monitoring for chiller units.

Monitoring of chilled water supply/return temperatures, etc.

Cooling Tower Control:

Start/stop control and status monitoring of cooling tower fans.

Fault alarm monitoring for cooling tower fans.

Manual/automatic control status monitoring for cooling tower fans, etc.

Start/stop and status monitoring of cooling water pumps.

Fault alarm monitoring for cooling water pumps.

Manual/automatic control status monitoring for cooling water pumps, etc.

Chiller Unit System Control:

First, when starting an additional chiller unit, it is necessary to determine which unit to start. Similarly, when stopping a unit, the same decision must be made. Second, when starting or stopping a specific chiller unit, it is essential to determine how many and which chilled water pumps, cooling water pumps, and cooling towers should be activated or deactivated.

(1) Chiller Priority Control Strategy: When the air conditioning load is less than the chiller unit's capacity, only the chiller unit operates. The ice storage device supplements the shortfall only when the air conditioning load exceeds the chiller unit's capacity.

(2) Ice Storage Priority Cooling Control Strategy: When the air conditioning load is below the maximum ice melting and cooling release capacity of the ice storage equipment, the load is first met by ice melting. When the air conditioning load exceeds the maximum ice melting release capacity, the chiller unit is activated to supplement.

(3) Fixed Proportion Cooling Control Strategy: This control strategy involves the ice storage device and the chiller unit outputting cooling load in a fixed proportion to meet the building's air conditioning load demand.

(4) Optimal Control Strategy: This strategy optimizes multiple control objectives (including daily operating costs, air conditioning load, remaining ice quantity in a cycle, and the number of chiller unit start-stop cycles) under constraints (such as maximum chiller output cooling load, maximum ice storage capacity, and maximum ice melting rate) based on dynamically predicted loads.