Batch calorimeter

Batch calorimeters are instmments where there is no flow of matter in or out of the calorimeter during the time the energy change is being measured. Batch calorimeters differ in the way the reactants are mixed and in the method used to detennine the enthalpy change. Enthalpy changes can be measured by the various methods... 

Reviews of batch calorimeters for a variety of applications are published in the volume on Solution Calorimetry [8] cryogenic conditions by Zollweg [22], high temperature molten metals and alloys by Colinet andPasturel [19], enthalpies of reaction of inorganic substances by Cordfunke and Ouweltjes [16], electrolyte... 

Heats of immersion were measured using a batch calorimeter (Pravdic, 1976). It was an isoperibolic instrument with a thermistor detector of an average sensitivity of i 1 m3 (which corresponds to an estimated 13 i3/cm ). A sediment sample sealed in a small glass bulb was brought into the microcalorimeter cell and carefully equilibrated to a... 

A) Batch calorimeters and B) Flow calorimeters. Both are used in calorimetry on fluids. 

Batch calorimeters have been widely used the disadvantage is that they yield only one measurement of the heat of mixing at a time. In the calorimeter of Larkin and McGlashan (61LAR1) the two pure components were confined over mercury and there were no vapor spaces. Mixing was accomplished by inverting the calorimeter. This calorimeter operated at near ambient conditions and ve accurate results (File Number LB3565). 

Clark et al. [146] were interested in the hypertrophy of brown fat in rats fed on highly palatable junk-type cafeteria food as a mechanism to dissipate the additional energy by increased thermogenesis. They measured heat flow rate in a rotating LKB batch calorimeter [28,147] and OUR in a stirred respirometer. The results for the dissociated brown adipocytes shown in Figure 51 demonstrate that the injection of noradrenaline stimulated the heat flow rate more than OUR and apparently gave a considerably more exothermic CR ratio of-1477 kJ mol O2. This result was interpreted to mean that the necessary ATP production had a reduced efficiency. 

Solution calorimetry covers the measurement of the energy changes that occur when a compound or a mixture (solid, liquid or gas) is mixed, dissolved or adsorbed in a solvent or a solution. In addition it includes the measurement of the heat capacity of the resultant solution. Solution calorimeters are usually subdivided by the method in which the components are mixed, namely, batch, titration and flow. 

Thermochemistry is concerned with the study of thermal effects associated with phase changes, formation of chemical compouncls or solutions, and chemical reactions in general. The amount of heat (Q) liberated (or absorbed) is usually measured either in a batch-type bomb calorimeter at fixed volume or in a steady-flow calorimeter at constant pressure. Under these operating conditions, Q= Q, = AU (net change in the internal energy of the system) for the bomb calorimeter, while Q Qp = AH (net change in the enthalpy of the system) for the flow calorimeter. For a pure substance. 

Generally, the temperature changes with time or, equivalently, with distance from the reactor inlet (for flow reactors). This change is usually controlled well in reaction calorimeters but can become uncontrolled in other conventional laboratory flow or (semi)batch reactors. The balance equations of a batch reactor for a single reaction of a-th order kinetics are given by ... 

If agitation fails during a semi-batch operation, the transfer of heat will essentially stop. The resulting increase in temperature depends on the concentration of the reactants at that moment, the global kinetics, and the mass transfer rate. The effect of the temperature increase is easily simulated in a reaction calorimeter both with and without addition of reactants. 

Usually, isothermal calorimeters are used to measure heat flow in batch and semi-batch reactions. They can also measure the total heat generated by the reaction. With careful design, the calorimeter can simulate process variables such as addition rate, agitation, distillation and reflux. They are particularly useful for measuring the accumulation of unreacted materials in semi-batch reactions. Reaction conditions can be selected to minimize such accumulations. 

There are a number of different types of adiabatic calorimeters. Dewar calorimetry is one of the simplest calorimetric techniques. Although simple, it produces accurate data on the rate and quantity of heat evolved in an essentially adiabatic process. Dewar calorimeters use a vacuum-jacketed vessel. The apparatus is readily adaptable to simulate plant configurations. They are useful for investigating isothermal semi-batch and batch reactions, and they can be used to study ... 

Figure 2. Heat conduction (Seebeck effect) batch mixing calorimeter for three samples and one reference channel. After loading and establishing baselines, the assembly is inverted to mix reactants and start heat production. (Reproduced with permission from Ref. 2. 1983, Alan R. Liss, Inc.)...

For the determination of reaction parameters, as well as for the assessment of thermal safety, several thermokinetic methods have been developed such as differential scanning calorimetry (DSC), differential thermal analysis (DTA), accelerating rate calorimetry (ARC) and reaction calorimetry. Here, the discussion will be restricted to reaction calorimeters which resemble the later production-scale reactors of the corresponding industrial processes (batch or semi-batch reactors). We shall not discuss thermal analysis devices such as DSC or other micro-calorimetric devices which differ significantly from the production-scale reactor. 

Zaldivar, J.M., Hernandez, H. and Barcons, C. (1996) Development of a mathematical model and a simulator for the analysis and optimisation of batch reactors Experimental model characterisation using a reaction calorimeter. Thermochimica Acta, 289, 267-302. 

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