The invention relates to a method for operating and/or monitoring an HVAC system (10), in which medium circulating in a primary circuit (26) flows through at least one energy consumer (11, 12, 13), the medium entering with a volume flow () through a supply line (14) into the energy consumer (11, 12, 13) at a supply temperature (T.sub.V) and leaving the energy consumer (11, 12, 13) at a return temperature (T.sub.R) via a return line (15), and transferring heat or cooling energy to the energy consumer (11, 12, 13) in an energy flow (E). A considerable improvement in the operating behavior of the system is achieved by empirically determining the dependence of the energy flow (E) and/or the temperature difference (AT) between supply temperature (T.sub.V) and return temperature (T.sub.R) on the volume flow () for the energy consumers (11, 12, 13) in a first step, and by operating and/or monitoring the HVAC system (10) according to the determined dependency or dependencies in a second step.

Method, systems, and devices for determining instantaneous heat exchange between an airflow and a heat exchange element of an HVAC system are disclosed. In some embodiments, methods and systems include receiving or otherwise obtaining airflow data, temperature and humidity data. The airflow data may be used to calculate the volumetric airflow rate, and the temperature and humidity data may be processed with enthalpy data to determine the change in enthalpy (h) of the airflow after encountering a heat exchange element. The instantaneous rate of heat exchange (E) between the airflow and the heat exchange element may then be determined from the volumetric airflow rate and change in enthalpy.

Method, systems, and devices for determining instantaneous heat exchange between an airflow and a heat exchange element of an HVAC system are disclosed. In some embodiments, methods and systems include receiving or otherwise obtaining airflow data, temperature and humidity data. The airflow data may be used to calculate the volumetric airflow rate, and the temperature and humidity data may be processed with enthalpy data to determine the change in enthalpy (h) of the airflow after encountering a heat exchange element. The instantaneous rate of heat exchange (E) between the airflow and the heat exchange element may then be determined from the volumetric airflow rate and change in enthalpy.

A thermal system includes a thermal control unit adapted to supply temperature controlled fluid to one or more thermal pads. The thermal pads may include an interior chamber for fluid circulation, an inlet and an outlet, and first and second temperature sensors positioned adjacent the inlet and outlet, respectively. Some pads include a valve adapted to control an amount of fluid flowing through one or more channels within the pad. The thermal control unit may include a controller that controls the fluid temperature based upon temperature readings from first and second temperature sensors positioned remotely from the thermal control unit. The thermal control unit may also include a valve that selectively controls the amount of fluid exiting the thermal control from one or more outlets based upon one or more temperature readings. The system may include one or more thermocouples with conductors placed on or in the thermal pads.

A method of controlling cooling water treatment may involve measuring operating data of one or more downstream heat exchangers that receive cooling water from the cooling tower. For example, the inlet and outlet temperatures of both the hot and cold streams of a downstream heat exchanger may be measured. Data from the streams passing through the heat exchanger may be used to determine a heat transfer efficiency for the heat exchanger. The heat transfer efficiency can be trended over a period of time and changes in the trend detected to identify cooling water fouling issues. Multiple potential causes of the perceived fouling issues can be evaluated to determine a predicted cause. A chemical additive selected to reduce, eliminate, or otherwise control the cooling water fouling can be controlled based on the predicted cause of the fouling.

A method of controlling cooling water treatment may involve measuring operating data of one or more downstream heat exchangers that receive cooling water from the cooling tower. For example, the inlet and outlet temperatures of both the hot and cold streams of a downstream heat exchanger may be measured. Data from the streams passing through the heat exchanger may be used to determine a heat transfer efficiency for the heat exchanger. The heat transfer efficiency can be trended over a period of time and changes in the trend detected to identify cooling water fouling issues. Multiple potential causes of the perceived fouling issues can be evaluated to determine a predicted cause. A chemical additive selected to reduce, eliminate, or otherwise control the cooling water fouling can be controlled based on the predicted cause of the fouling.

A method of controlling cooling water treatment may involve measuring operating data of one or more downstream heat exchangers that receive cooling water from the cooling tower. For example, the inlet and outlet temperatures of both the hot and cold streams of a downstream heat exchanger may be measured. Data from the streams passing through the heat exchanger may be used to determine a heat transfer efficiency for the heat exchanger. The heat transfer efficiency can be trended over a period of time and changes in the trend detected to identify cooling water fouling issues. Multiple potential causes of the perceived fouling issues can be evaluated to determine a predicted cause. A chemical additive selected to reduce, eliminate, or otherwise control the cooling water fouling can be controlled based on the predicted cause of the fouling.

A method of controlling cooling water treatment may involve measuring operating data of one or more downstream heat exchangers that receive cooling water from the cooling tower. For example, the inlet and outlet temperatures of both the hot and cold streams of a downstream heat exchanger may be measured. Data from the streams passing through the heat exchanger may be used to determine a heat transfer efficiency for the heat exchanger. The heat transfer efficiency can be trended over a period of time and changes in the trend detected to identify cooling water fouling issues. Multiple potential causes of the perceived fouling issues can be evaluated to determine a predicted cause. A chemical additive selected to reduce, eliminate, or otherwise control the cooling water fouling can be controlled based on the predicted cause of the fouling.

Systems and methods are provided for evaluating performance of a heat exchanger, such as a condenser, using rules-based logic. A plurality of sensors can measure various operating properties of the heat exchanger and transmit corresponding measurement information to a controller. The controller can (i) evaluate the measurement information for a plurality of rules in which each rule considers an operating parameter of the heat exchanger that is based on the measurement information to provide a set of operating values; (ii) compare the set of operating values to a rules matrix in which each of a plurality of possible diagnoses for the heat exchanger are associated with a corresponding set of predetermined values from a set of the plurality of rules; and (iii) based on the comparison, determine at least one likely diagnosis for the heat exchanger from among the plurality of possible diagnoses.

Systems and methods are provided for evaluating performance of a heat exchanger, such as a condenser, using rules-based logic. A plurality of sensors can measure various operating properties of the heat exchanger and transmit corresponding measurement information to a controller. The controller can (i) evaluate the measurement information for a plurality of rules in which each rule considers an operating parameter of the heat exchanger that is based on the measurement information to provide a set of operating values; (ii) compare the set of operating values to a rules matrix in which each of a plurality of possible diagnoses for the heat exchanger are associated with a corresponding set of predetermined values from a set of the plurality of rules; and (iii) based on the comparison, determine at least one likely diagnosis for the heat exchanger from among the plurality of possible diagnoses.