Simulation of heat exchangers and heat exchanger networks with an economic aspect

Research of variable characteristics of heat exchange equipment

“…In the case of fixed flows, the heat transfer coefficient is affected only by a change in the temperature of the heat transfer fluids. From (5) follows…”

“…It should be noted that at a constant primary coolant temperature tp1 = const, the variable parameter of the heat exchanger NTU(t) slightly deviates from constant NTU for any changes in flow rates and the heat capacity of the heat exchanger [17] and can be determined by (5) in the installation conditions. This is especially important when the operating temperature graph deviates from the accepted one as well as when calculating the operating modes of the tied heat exchangers where the number of unknowns is much greater than when calculating a single heat exchanger.…”

“…To assess the efficiency of heat transfer processes in variable operating modes, the values used in the theory of heat exchangers are widely used, which include heat exchanger efficiency , log average temperature difference t, heat exchanger surface F and the number of heat transfer units NTU. These indicators are widely used for calculating and comparing the efficiency of heat exchangers of various types [1,2] in heat and power [3][4][5], aviation [6], chemical industry [7], in ventilation and air conditioning systems [8][9][10][11][12]. The convenience of using dimensionless complexes, such as NTU, is in the assumption that the heat transfer coefficient and the efficiency of the heat exchanger are practically independent of the temperatures of the heat exchanging media [13,14].…”

“…The convenience of using dimensionless complexes, such as NTU, is in the assumption that the heat transfer coefficient and the efficiency of the heat exchanger are practically independent of the temperatures of the heat exchanging media [13,14]. This allows to reduce the number of unknown variables which is especially important when calculating the associated heat exchanger systems, however, it is often necessary to solve the problem by the method of successive approximations [5,12,15]. However this assumption is valid in a fairly narrow range of temperature variation of coolants, therefore the use of constant parameters has often been criticized [2,12,16,17].…”

Study of Heat and Mass Transfer Through an Earth to Air Heat Exchanger Equipped with Fan in South West of Algeria

“…Jiang et al [11] proposed a new methodology for heat exchanger network retrofit to fully evaluate the performance of a heat exchanger network. Kayabasi and Kurt [12] derived relations between effectiveness and expense coefficients. They prepared an economic simulation model to simulate the heat exchangers in all flow types and monitor the savings in a facility.…”