Sensible heat, defined

Next, we construct a table of exchangeable heat loads TEHL to determine the heat-exchange loads of the process streams in each temperature interval. The exchangeable load of the uth hot stream (losing sensible heat) which passes through the zth interval is defined as... 

The energy term E must be defined to calculate energy-scaled standoff R. The energy term represents the sensible heat that is released by that portion of the cloud contributing to the blast wave. Any of the accepted methods of calculating vapor cloud explosive energy are applicable to the Baker-Strehlow method. These methods include ... 

If the reaction is conducted both adiabatically and witli stoichiometric air. tlie resulting temperature is defined as tlie theoretical adiabatic flame temperature (TAFT). It represents tlie nia.xinuuii temperature tliat tlie products of combustion (flue) can acliieve if the reaction is conducted both stoichionietrically and adiabatically. For tliis condition, all tlie energy liberated from combustion at or near standard conditions (AH°c and/or AH°29s) appears as sensible heat in raising tlie temperature of tlie flue products, AHp, tliat is ... 

The use of mean heat capacities often facilitates the calculation of sensible-heat changes mean heat capacity over the temperature range r, to t2 is defined by the following equation ... 

The water removed from the air AT = Yabsin — Yabsout is absorbed by the desiccant. The system of absorbed and regenerated desiccant has the potential to remove the latent enthalpy A IIlat = Mair reg AY h iat(T) from the air flow. Neglecting the small amount of sensible heat of the absorbed vapour, the storage capacity SC for dehumidification enthalpy per volume desiccant Vdes can be defined as... 

The available heat is defined as the quantity of heat released within a combustion chamber minus (1) the sensible heat carried away by the dry flue gases, and (2) the latent heat and sensible heat carried away in water vapor contained in the flue gases. Thus, the available heat represents the net quantity of heat remaining for useful heating. 

In assessing the ability of an HVAC system to maintain acceptable humidity levels in the building, the more important performance parameter is the sensible heat ratio (SHR) of the equipment. The SHR is defined as the ratio of the sensible cooling load to the total cooling load. Improved latent performance is characterized by a lower SHR. Defining the relationships between SHR and other dehumidification indices is also convenient. In particular, the latent heat ratio (LHR) can be defined as the latent cooling load fraction, and the latent to sensible ratio (LSR) can be defined as the ratio of latent load to sensible load. These ratios appear as... 

The relationships among the psychrometric states, loads, and sensible heat ratio are shown graphically in Fig. 3. For a given pair of entering and leaving air states, sensible, latent, and total loads are proportional to the differences in temperature, humidity ratio, and enthalpy, respectively, as shown in the figure. The SHR is defined by the slope of the line connecting the two points. 

We used HSC as the thermodynamic database [5]. Table 1 lists the enthalpy balance (heats of reaction, sensible heat, and latent heat for phase changes) for both the endothermic and the exothermic reactions defined above. 

For consistency with later examples in which heat of dilution effects are important, we read all the enthapies from the steam tables, which have a reference state (where H is defined to be zero btu/lb) corresponding to saturated liquid water at its freezing point. In Example 8.4-1 on p498, Geankoplis works a very similar problem in which all enthalpies are calculated using the conditions of the liquor as the reference state. Then (by definition) H in (19) is zero the enthalpy of the feed // differs from that of the liquor just in sensible heat, which can be estimated as (8.4-... 

Direct drying is the process of removing this liquid via the mechanism of convective heat transfer. The heat input usually takes the form of preheating a carrier medium (such as air, evaporated solvent or an inert gas) that transfers the sensible heat and acts as an absorbent to take away the liquid in the vapor form. The carrier medium can hold a fixed amount of liquid (saturation) at its defined temperature. The solids release the liquid to the carrier medium as a function of saturation and equilibrium. In essence, the heated gas has a higher saturation affinity for the liquid in the vapor form than does the solid at the gas temperature. 

In many practical appliances, which range from steam engines to internal combustion engines, the carbon dioxide and water products are released to the atmosphere at comparatively high temperatures and the heat that these gases hold above the reference temperature of 298.15 K is lost. This heat consists of both the sensible heat i.e., the heat carried by the substance - its heat capacity ) and the latent heat of condensation of the steam. For practical engineering purposes, it has become customary, therefore, to define a lower heating value (LHV), which corresponds, arbitrarily, to the maximum heat recoverable when the reaction products are emitted at 423.15 K. 

TOTAL HEAT (ENTHALPY) - Total heat is the sum of the sensible heat and latent heat in an exchange process. In many cases, the addition or subtraction of latent and sensible heat at terminal coils appears simultaneously. Total heat also is called enthalpy, both of which can be defined as the quantity of heat energy contained in that substance. 

Exothermic processes should supply all the heat requirements for the process. Related topic thermal pinch, Section 1.11. Based on the conservation of energy, the heat acquired/lost by a stream = the heat transferred to/from the stream. For sensible heat, q = mass flowrate (F) X heat capacity per unit mass (Cp) X AT = heat transferred = UA MTD. This is sometimes rearranged to define a thermal heat transfer unit, THTU, = AT/MTD = UA/F c. ... 

On the other hand, an endothermic reaction has a positive enthalpy of reaction. It can only take place if there is a particular amount of energy available to absorb, which is equal to or larger than the value of the enthalpy of reaction needed. The enthalpy itself is temperature dependent and called sensible enthalpy or sensible heat, and is defined as the amount of heat required for raising the temperature of a substance by 1K without changing its molecular structure. 

Qg = sensible heat transferred to the gas phase Qt = total amount of heat transferred G and L = mass velocities of the gas and liquid phases Cg and Q = heat capacities of the gas and liquid phases, respectively a = quantity defined below... 

So far, we have considered neutral conditions in the surface layer. In cases with light to moderate wind speeds, the effects of surface heating and cooling also become rel-evant. Consequently, the virtual sensible heat flux w9m at the surface needs to be considered as an important variable as well [because it impacts on the buoyancy term in Eq. (3)]. The combination of surface heat flux with friction velocity defines a characteristic length scale L, given by... 

Drying methods have been evolved aroimd every product s specific requirement. The process takes many forms and uses many different kinds of equipment. In general, drying is performed by two basic methods (a) adiabatic processes and (b) nonadiabatic processes. In adiabatic processes, the heat of vaporization is supplied by the sensible heat of air in contact with the material to be dried. In nonadiabatic processes, the heat of evaporation is supplied by radiant heat or by heat transferred through walls in contact with the material to be dried. Dehydration may also be accomplished by mechanical dewatering. However, in this chapter, dehydration due only to adiabatic or nonadiabatic as defined above will be described. 

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