Method and arrangement for controlling the temperature of the outstream flow from a heat exchanger and measuring produced heat

A device for controlling the temperature of at least one outbound secondary flow (2) from a heat exchanger (1) in a secondary circuit by means of a primary flow (3) in a primary circuit passing through the heat exchanger, where a control unit (7) controls a regulatory member (5, 11) arranged to regulate the primary flow,

• characterised in that
• temperature gauges (8, 9) are arranged to measure the temperature of the primary flows inbound to (3i) and outbound from (3u) the heat exchanger (1) for determining the enthalpy difference between these flows,
• a flow gauge (4) is arranged to measure the flow (qsec) of the secondary medium (2),
• difference pressure gauges (6) are arranged to measure the pressure difference (ΔP) in the primary medium (3i) across the regulatory member (5), or that a flow gauge (12) is arranged to measure the flow (qprim) of the primary medium (3),
• and that the output signals from said gauges (4,8,9,12) are arranged to be transmitted to the control unit (7) for controlling the regulatory member (5, 11), wherein the primary flow (3) is arranged to be controlled in dependence of the secondary flow (2), so that the power transferred between the heat exchanger and the primary flow (3) substantially corresponds to the sum of:
• 1) the power needed to change the temperature of the secondary medium from the current inbound temperature Tsec—in to the desired outbound temperature Tsec—out—set point and
• 2) assumed power demand for compensation of stored energy in the heat exchanger (1), and
• 3) assumed leak power from the heat exchanger.

A procedure for determining the power and heat quantity transferred to a heat exchanger via the primary circuit of the heat exchanger by means of a regulatory member (5,11), regulating the flow through the primary circuit, which member (5, 11) is controlled by a control unit (7),

• characterised in that,
• the enthalpy difference (Δh) between the primary flow inbound to (3i) and outbound from (3u) the heat exchanger (1) is determined, that the pressure difference (Δpregulatory—member) across, and the medium temperature (Tmedium) in, the regulatory member (5, 11) with known flow characteristics stored in the memory of the control unit (7) are determined, that the density of the primary medium is stored in the memory of the control unit (7), that the enthalpy difference (Δh), the pressure difference (Δpregulatory—member), the temperature (Tmedium) and the degree of opening (a) of the regulatory member are registered, which parameters together with the flow characteristics and the density stored in the memory of the control unit, provides a value of the power and heat quantity yielded by the primary circuit, characterised in that,
• the determined value of the power and heat quantity yielded by the primary circuit are checked against simultaneously valid value of the power and heat quantity absorbed by the secondary circuit, which are calculated from the parameters enthalpy difference Δhsec between inbound and outbound secondary flow and flow msec, which are stored or determined in the control unit, wherein an alarm is provided to the environment via communication means if the values for power and heat quantity yielded and absorbed by the primary and secondary circuit, respectively, deviate from one another by more than a predetermined acceptable value.